short answer: by the time you get done the conversion, you will have spent 2/3 the cost of buying an electric...and you wont end up with a very reliable model.

long answer: yes it can be done. Homemade motor mount isn't that tough to figure out. Brakes are tricky...the center trans spins freely in one direction (so no motor braking or reverse)
You can lock the center trans together with JB weld to make it act like a simple spur gear. That will allow the electric motor to act as your brake and allow for reverse. Or you can use a "Y" harness for the ESC and the throttle/brake servo. This will let you keep the trans stock, and still have mechanical brakes. But you wont have reverse.

Only a few EPX PRO parts will work. The electrics use a plastic chassis and fully different center driveline, The diffs are the same, but the suspension arms and hubs are not (pivot ball on the nitro, "C" hub on the electric)

Best bet, put your nitro on ebay and try to get $100 out of it (after shipping and ebay fees) and put that towards a EPX Pro (just a bit over $200)

To get a epx pro plus a lipo and lipo charger, you will need around $300.

Again, by the time you have bought a brushless ESC, motor, battery...and made custom motor mount and other small custom bits, you will have spent around $200 anyway.