well it sounds like the speed controler could be bad...and that is what fried the motors. brushed motors do wear out over time, but 2 dying back to back is rare.
to answer your question on brushless upgrade:
the simplest thing would be to get the speed control and motor from the brushless version of your truck....the epx PRO.
Brushless motors work very different from brushed...and your speed control (ESC) will not work with a brushless motor.
the epx pro uses a ezrun 35amp brushless esc and a novatech 540 3300kv brushless motor.
Another option is to find a used traxxas VXL 3s system.(stock in the traxxas brushless 1/10 scale models)
you will be looking at around $100-$130 to get a brushless esc and motor.
My suggestion if that cost is to great:
find a used traxxas xl-5 speed control and grab a new venom fireball 21t motor like this one: http://www.ebay.com/itm/Venom-1315-F...item5ae547e4a7
or a new ECX electrix speed control (used in the torment truck) and the 20 turn (T) 540 brushed motor that is also on the same truck.
Brushless upgrade IS worth the extra cost. A brushless motor doesnt wear out and its more effiecent and thus gets better runtimes and slightly more speed. but I know not everyone can afford it, and a decent brushed setup is still lots of fun.