check engine light came on and speedo stopped working @ the same time.

'99 4.0 . I'm wondering if anyone else has had a simalar problem? I had a local shop put a new clutch in it for me recently and am now having some regrets.I'm not sure, but I have been thinking that they may have damaged the wiring going to the speed sensor, although I can't find any visable damage. I put my friend speed sensor from his tj into mine in an attemt to find out if my sensor was bad (did'nt help any) and now his jeep does the same thing. did my computer break his sensor? Is there some sort of computer reset that i'm unaware of? apart from the engine light and not having a working speedo, my jeep now stalls when coming to a stop and the cruise control won't work. any ideas? thanks.