I'd say just go down to Funan Center, there's quite a few good camera shops around there including Alan Photo, John 3:16 and SLR Revolution. I doubt anywhere will have the old 5D, but you can ask to try the 5Dmk2, I believe the bodies are almost the same. Don't forget to try the Pentax K-7 too while you are there.
FF is nice, but you have to be prepared for the big investment into more expensive lenses. IMO I wouldn't recommend it unless you are really crazy into photography, or planning to be a professional photographer, or you are just filthy rich. There are after all plenty of very enthusiastic photographers still happily using APS-C DSLRs.