I think that's a great situation for getting feet wet in Wedding photography, personally.
My niece got married last year and asked me to do her's... I actually told her she should get a professional, and made the B&G think about it for a week. They were on a tight budget, I guess, and weren't expecting anything more than snapshots... so that took the pressure off of me. But, of course, I wanted to do the best I possibly could (because if I just took snapshots, I wouldn't be happy with my own work.)
Luckily I had a couple months to read up on techniques, the basics of posing for portraits, shots to watch for, etc... but when that day came I was BUSY. Everything turned out well, but I DID make some mistakes. It was a good learning experience. But I think if you've been honest with bride and groom, and they realize you're not a pro-wedding photographer you're fine.
I had another friend that had been there ask me to do their photos for upcoming wedding, but I turned them down. I told them they should get pro. too, but I would be happy to be secondary photographer to take candids to get shots pro might not. (someone who knows the familys well can often capture great shots, as they know who are close to the bride and groom) I definately respect the pro wedding photographers after my experience! If I were to try to go into this seriously, I would find a local pro and try to work a few weddings with him.
As far as PP, I used DPP mostly (Canon's) when I did the wedding... did some with the Lightroom beta I had also. DPP worked really well for me, and was glad I shot mostly in RAW, becaue it helped me immensely with white balance for ceremony shots, also for rating images helped seperate the duds from ones I took time to process.