They can be added after the fact, but keep in mind that the deck might not be reinforced adequately in the area you want to put them, and so they may require some heavy backing plates. The coring in the Rangers was plywood in some areas, so if you can determine that and its condition that will be helpful in deciding what measures to take. Sealing the new track mounting holes is crucial, you don't want to compromise the core in the deck. Drilling oversized holes, filling with epoxy and then redrilling to size is the best way to do this. There will be some gains in performance if the tracks are properly placed. It would be good to find some other 33s and get some dimensions there.
Another issue that often arises when tracks are added is that now the headsail needs to come inboard of the lifelines - another chore for each tack unless you steer slowly through the turn and sheet in quickly enough to keep the sail inboard (practice, practice!) Sometimes the lifeline configuration can be changed if necessary.
Portlights: the original Ranger ports were pretty notorious for leaking when old, so that's probably why it's been changed - if not leaking now I'd leave it. If it's the look you don't like, then there are some aftermarket suppliers (pricey) that do a great job.
Most recognized headsail furlers will do a good job for you, with Harken a pretty safe bet all round for whatever gear you need, though there are others that are less costly for less demanding needs. I know many people happy with Furlex, for example, and I hear the installation of them is pretty simple.
Welcome to our world, and good luck!