Well, first of all, the appropriate answer to any question that begins "What does the UCC believe/think..." (or "What is the UCC's stand on...") is "It depends." See, the UCC has very few "official statements." Our basic unit of life is the local congregation, and we're essentially autonomous in our governance. Yes, ordination and authorization for ministry happens through the association (in cooperation with a local church, and possibly also a fourth institution, such as a hospital), and yes, the national setting of the UCC (or some part of that national setting) does sometimes makes statements/pronouncements on this matter or that. But, local churches aren't bound by these decisions - they needn't "obey" or agree with what's said.
Every two years, the UCC comes together in what is called a "General Synod," which has delegates from every association, and we vote on "pronouncements" and "resolutions." The thing is, General Synod speaks TO the church at large, not FOR the church. This means that when we get together, we're talking about all this stuff for each other, and guiding the work of the national setting(s) of the church in between General Synods. STILL, local congregations aren't "bound" by these decisions in the way that a Lutheran or Episcopal church might be.
All that being said, at General Synod XXV in Atlanta (Atlanta, baby!) in 2005, the General Synod did vote to, among other things, "calls upon all settings of the church to engage in serious, respectful, and prayerful discussion of the covenantal relationship of marriage and equal marriage rights for couples regardless of gender..." (see the full pronouncement here). It was a contentious and difficult decision. We lost some churches over this (or, perhaps more precisely, over issues of biblical interpretation that led to the passage of this resolution).
Yet no church is bound by this. In fact, it would be perfectly fitting of our polity for a church to engage in just such a discussion and come to the conclusion that marriage should be between a man and a woman only. Obviously, some churches in the UCC do come to this conclusion.
As to whether or not the congregation I serve has a stance on same-sex marriage, at this point I can only point to our Open and Affirming statement, adopted by the congregation in 2000: "First Congregational, United Church of Christ in Red Oak is an active and dynamic congregation with a rich history and an exciting ministry to the community. We welcome into this community of faith, and affirm the participation in all aspects of church life, persons of every age, race, gender, nationality, ability, and sexual orientation. We will empower ourselves, our children, and one another to be fully present in the world, living in Christ's image and striving for justice and peace." From this statement (and the text I bolded), and from what I know of the views of most of the people at church, it seems logical that we would affirm same-sex marriage. But until the congregation has a chance to speak its mind, I would hate to speak for them or name this as their reality.
And in fact, due to a series of interesting circumstances this spring, our congregation has not technically addressed this issue in a formal sort of way. We will do so on May 17, at forum following worship, and I would covet your prayers as we discern the ways that God is calling us to live into this commitment. I suspect I know how much of the conversation is going to go, but it's also important for us to check in periodically about how we are living out this commitment.
The church's normal policy regarding marriages held in the church or done by the pastor basically comes down to "the pastor's discretion." Which means it's up to me, and obviously, I consult with the board, if only to inform them of what I'm doing. To be truthful, up until this year, weddings have not really been a big deal here. I've done 1 a year, or 4-5 a year, but never a whole bunch. With Iowa's marriage equality ruling, I expect that may change. Finding a balance of serving this need while also serving the not- insignificant needs of the congregation and my own spiritual/familial needs will definitely be a priority in the next several months.
I must also disagree with you, dear PastorJoelle, when you say, "I'm just saying it would be nice to have a little church support and guidance in this matter other than - 'Do whatever you think is best.'" I love the autonomy of the UCC and while I am sometimes tempted to wish for a bishop's authority, it is never for very long (Bishop Yvette Flunder would be AWESOME, but what if I ended up having to submit to someone like Peter Akinola? No thanks!) The UCC takes seriously the "responsibility of every generation to make the faith its own" (it's from our Constitution) and I really appreciate that we have to do the work...and that we are are responsible for the work.
In some ways, it is easier to have an answer one way or another - this way you can agree gracefully, submit gracefully even if one disagrees, or to choose to faithfully dissent. But, this is not our way in the UCC. It's a lot harder, and let me tell you - lots of us get really sick of being in the in-between time where all our answers are tentative at best and we have to keep fighting the same battles over and over (and over and over) again. But, that's the work of Christianity - and a substantial part of the work of the UCC is to disagree in love and find a way to stay together, united in Christ even if not much else.
PastorJoelle, I am keeping your congregation and your denomination in my prayers in this season. As well, I will remember all those who live in tension between their personal faith convictions and the "official" stance of their denomination/tradition.