SO, i just ran around day to figure out why my car wouldnt pass smog.

1st, went to get it smogged, they sent me to another place for a test, then the test place sent me over to a referee because i dont have the stock motor. I have a 1994 Civic EX with a 1995 GSR motor in it. The referee said that the cars emissions were too high and then told me to go over to a shop to get a diagnosis. SO i went in for the diagnosis. My car needs a new cat and a new O2 sensor, but didnt specify which one. He also said that the ECU might be throwing off the wrong signals or something like that... my bank account isnt hudge and i need to get this car to pass smog, PLEASE HELP. what do i do, i know i need a new cat, im going to buy a universal one and install it, but i dont know how to install a new o2 sensor and i need the one for the acura correct? and if the ECU needs to be reprogrammed or whatever, how much is that going to run me?

if you can, please answer all points...

adam