92 jeep cherokee starts but wont stay on?

So heres what happened. My brother saw smoke coming from the ceiling, (no headliner), and noticed the module on ceiling by the lights caught fire. they cut the wires from it and left it alone. they later spliced the wires together and now the jeep starts everytime but immediatly shuts off. Took it by a local mechanic and he says the module needs to be replaced and a few other things and quoted around $400+......another guy says that it can be bypassed and the computer can be reset or something.....anybody have an idea as to whats going on or what i can do or try??? any info will help. thanks