I'm sorry, I don't have the chords you needed, but I have a few tips for playing by ear in church.
When I was about 13 I had just started playing, and church helped me grow as a musician.
First, since you are playing acoustic, and just starting out, get a capo (if you don't have one), and learn to use it. This will allow you to play every song, and not feel silly for sitting up there polishing your guitar during your piano player's odd-key masterpiece. then later on, you can pick up all the funky barre chords and inversions (but, by all means, go ahead and start learning them).
Also, my dad is a bluegrass nut, so he taught me all my open chords first, and my rhythm strings (these are what you hear in your most basic country song--the root and the fifth--dum--digga--dum--digga). You may never actually use these like that in church (depending on your church--I grew up in a southern Pentecostal church and I used them all the time!), but they help give you an understading of note placement on the neck, and help fill out your rhythms.
If you have another guitarist there, ask questions. Stick to that person like that dryer sheet that you didn't know was hanging out of your pant leg on Sunday morning.
And just jam with people as much as possible. Playing in a church, or with others is the best way to season yourself.
Hope that helps some.
