The 'squirt in my car was already assembled when I bought it, but If you're an electronics wiz (or ****, just good at soldering) you could probably assemble a unit yourself. Or buy a prefabbed unit.
Definately check out the links I posted to see what all is involved, and it is...pretty involving.
P.S. A guy here in Michigan who is a MS guru had a bulk buy on probetalk a while ago. For a nice chunk of change, they would outfit a stock probe ECU with a MS, so while the stock computer controlled Idle, fans, and other smaller functions (which it does extremely good, even my probe doesnt start and idle the best...it's rather annoying on cold days) the MS controls Fuel and Spark.
I'd try contacting him on AIM (Ryanpzz), ask him what MS could do for a F/I SHO, and if he knows how complex/costly it would be.