-first off, I think that a 55 gallon would be perfectly fine. ( in my opinion, but its good to have a few perspectives )
-getting live rock from the LFS is usually more reliable, so if your getting it secondhand I would strongly suggest to inspect it closely.
-I would recomend a sump
im not good with the plumbing part either, but here's a link :
http://saltaquarium.about.com/od/sum...Box_Setups.htm
-google is also good for info on sumps
-in my opinion RO isnt needed, and I just use declorinated tap water, but its your tank, so do what you think is nessesary
- Hope this helped, and good luck
