Electrical problem
1994 Jeep Laredo 6 cyl Four Wheel Drive Automatic

I have a jeep cherokee laredo thats strats but only runs for 2 sec and shuts off. I was told by a mech that it was security system and to take to dealer and get key and flash computer. I took to dealer and they said that it was control module. they qutoed me 1000. I see that you can get pre programmed modules on lin efor about 250 and they are under passenger seat. This seems like a very easy install. I have replaced transmissions and all kinds of other car components, Anything tolook out for or any other reasons to think I could not do this.