Replacing all theme files

[Igal]

Hello,

As I've mentioned in this thread: viewtopic.php?f=17&t=10626&p=51845#p51845
I'm facing some strange problems in my wp admin, I also for instace have a strange problem with the Rss feed icon which has moved to the left (above the header - screenshot attached)

I'm sure that I caused it by changing one of the files - I don't know which.
I think that what can help me, is to download the new wordpress 2.8 (I'm using the 2.7.1) + to replace the theme files (I have the same copy which I installed 4-5 months ago)

My question is: If I'll do that, will that affect anything on my blog? For instace:
1. Posts
2. Categories (and their structure)
3. Comments
4. Plugins
5. Ads (adsense)

P.S - is there a later version of the Church theme?

Thanks a lot.