My suggestion would be:
Install highway pegs and new grips - pretty much bolt on
Replace pipes (nothing fancy, just something with a little more power and a deeper, throatier sound) - this can also be a bolt on, not too hard assuming you don't break any studs and you get a set that don't require rejetting the carbs
Replace and/or chop rear fender
Repaint fenders and tank (solid black) - paint is pretty easy, and easy to fix if you screw it up, of course if you're going to chop your fender you don't want to paint first
Replace seat upholstery - this can be cheap and easy
Replace dual seat with low-profile solo seat - this can require quite a bit of fab work
Replace speedometer (or perhaps the entire electronics cluster) - this can be easy or hard, depends on what you want to put in it's place. Drop a Vapor in there and it's pretty simple but you probably wont like the look. Think brackets, mounting cups, cables, wiring...
Install larger gas tank (possibly from a larger Vulcan? Don't know if this is possible) - cutting, welding, relocating other components
Replace stock bars with 14" apes. Possibly with internal wiring. - not too hard if you can get the longer cables you'll need. Not much work here just money. This one's last simply because I don't like apes.