There's a couple of things and a couple of ways to do the swap.

Things that has to be changed includes =
- Headers
- Distributor (internal vs. external)

Those are the main things that you have to change out in order to get the car running. You can change the intake manifold to a s13 manifold, which I consider the right way to be done; however you can retain the stock s14 intake manifold. Using the stock s14 intake manifold will mean that some plugs will be left unused.