Dodge Colt 1992 check engine light

I had to replace the ecu on my colt 100e, 1.5l efi. When I put the rebuilt computer in (it cost me over $500 for the computer - no labour - which seems a little outrageous to me) and started the engine, a couple of things occured:
1. The engine wouldn't idle, so I had to increase the idle speed a ton
2. Engine was mis-firing, so had to play with distributor and advance the spark a tad (we'd had the distributor out, as we initially thought that was the issue)
3. The "Check Engine" light came on and does not go off

Any ideas on how to reset the light, or on what may be causing it to stay on?

Thanks a ton,
Marty.