Trek 750 are hard to find, and tend to be expensive. They are double butted cro-mo. The lower numbered 700 multitraks are plain guage cro-mo.
I have one that I am building up as a loaner for a friend that lent me a bike for several weeks when I was in MA. He is a bit shorter than I, so nothing I had would fit him. I scored a '92 Trek 750 in his size for $50- off CL - poor ad, lousy description, awful pictures. Bike was in excellent condition except for the rear shifter was shot. I am putting a 28mm tire on the front for better balance - street only, along with drop bars, 3X7 Brifters and Shimano derailleurs from a scrapped out Galaxy SC2. I'd pay $300+ for one in similar condition in my size.
1993 was the last year of lugged and brazed 750 (and 790, 930, 950, 970, 990, 520) Treks. Too many of us, the lugged and brazed are more desirable than the TIG welded ones.
Regarding wheels, what is your budget? Low, these are fine:
Sun/Shimano CR18 Wheel Set 700c Silver
If your budget is a little more:
Wheel Master Velocity Chukker Wheel Set - 700c x 35, 9-Speed, 36H, QR, Silver NMSW or
Wheel Master Velocity Dyad Wheel Set - 700c, 36H, 9-Speed, QR, Silver MSW or
Wheel Master 700c Hybrid/Comfort Wheel Set - Velocity Dyad Rim, 40H, 8/9-Speed, Black MSW
The Velocity rims are much nicer than the Sun rims. I build my own wheels, I am big guy and like 40 spokes per wheel. I use the Wheelmaster 40H hubs, which are a copy of a Phil Wood: the rear hub even comes apart the same way with a pair of 5mm hex keys; Wheelsmith spokes and Velocity Dyad (700c) or Aeroheat (26") rims.