Next time start your own thread if you have questions. But even better, do a search before asking questions. Clearly people do engine swaps everyday so one would assume that the answer would have been covered about 100 times already.
It all depends on what vtec engine you're talking about. If you're talking about a SOHC motor, like the D16Z6, then it will be easy to do. If you swap in a DOHC it will be hard as hell to do. No, I'm just screwing with you; it will be just as easy. For a D16Z6 look here:
http://www.hondaswap.com/~pills/obd1guide.html For B-series look at this:
http://www.ff-squad.com/tech/wiring/wiring.92-95.jpg You can use either a complete harness form the new motor or your existing harness. If you use the CX one, then you need to convert the 1 wire O2 sensor to a 4 wire one; here:
http://www.hybridautomotive.com/tech/o2/#one