I asked my LBS about that very thing a month or so ago, and they told me all the things you mentioned, as well as a new bottom bracket - about $300 worth of equipment when it was all over. I ended up opting for replacing my 8 speed 12-26 with a 13-30 spent about $200 instead (had to replace rear derailleur with long cage model) and have yet to have to push the machine up a hill! I'll admit, Dallas doesn't have quite the hills SA does, but there definitely are some, especially south of town..
Now if I can get rid of a few pounds (me, not the bike), it should be even easier !