buying a 91 coupe

A turbo swap can be easy and cheap. Or it can be a pain and expensive. It's all in how you go about it. It seems the easiest way is to find a full donor car, that way you have all the possible things you may need right in front of you. When you don't have all parts needed, finding them individually can be very hard or expensive, or both. The website he gave you is very easy to follow and provides great information. Google '2.3L Webring' and you'll find plenty more sites similar to that one.
If you are sure you're going to swap in a turbo engine, don't even bother modifying it in N/A form, it's worthless.