sounds like sadiekate has got you covered with the rim/brake situation...

i had a thought when you mentioned you have an "old" trek...is it just sittin' there? can you swap the components from that to a shiney NEW frame (or a used one with fresh paint ) just to get her out on the trails to see how she does? then you can start applying newer components accordingly?

my mtb has some middle of the line components and some higher end components for a couple of reasons...one example: my original brakes were avids but i got the middle of the road levers because they were LIGHTER!!! but that was because they were plastic...which was fine for me because i was a nooobie and pobably not going to be as hard on them...well time has past and i am racking up the miles so for Christmas hubby and i treated ourselves to hydro brakes...had to go with the better ones there

so you see...you have many, many avenues you can go without braking "her" bank and getting her a nice, beeeeutiful ride!!!!