Depends on what route you want to go.
You will need an obd2-obd1 conversion harness for sure with the p28. You have tuning options such as Crome, eCtune, Neptune, Hondata, etc. Some are free (Crome) but have less options unless you upgrade (Crome Pro), some cost a few hundred (Hondata), etc. Some have more features than others (more tuning options).
It really depends on what you want, how much you're willing to spend, etc. I think many can agree though, tuning is THE MOST important part of any setup. One mistake with tuning and you might as well have another motor on hand.
Myself, I am tuned on basic Neptune. I bought a chipped P06 from some guy on eBay who even puts his own basemaps on there for you. I had him put a basic basemap on there so the car would at least be drivable to the tuner's location, where they would tune the car professionally on the dyno (and street tuned) from there.
Oh, and this is my 2000th post.
lol