Awesome you got a wheelchair to convert
I've been working on mine for about 8 months now.
First thing I did when I got it was toss out the oem joystick and speed controller/motor driver (didn't throw away, just not using it). Not sure how yours is setup but mine needed a special programmer that you can rent or buy to change the acceleration, speed, and other settings. The current settings were extremely sluggish and slow.
I bought a sabertooth motor driver and it's been pretty awesome.
Yeah...get a multimeter and if you can on that has the continuity 'beeper' ...really helpful.
Post some pictures if you can, would like to see your progress