Rear brake conversion is possible, but you pretty much need to find a donor car and pull out calipers, rotors, e-brake cable (yep, the whole cable going down to the e-brake pulley inside), and probably something else I'm forgetting. A bit of a hassle, but there are a few guides on this in the DIY section
HERE (also has a bunch of write-ups on suspension)
As for the wheels, you're going a bit too wide with the 8.5" rims. From what I've seen, Gen4 Camry can accommodate up to 7" rims (215mm width). Anything wider than that, and you run the risk of needing offsets and/or other issues.
For suspension, you just gotta figure out what you want to do with the car: keep the stock ride and feel, drop the car, or firm up the suspension. There are struts and springs for either case.
Hope this helps.