Do I need to do any shoulder rehab if I dislocated it and popped it back in on my own?

Yes. Physical therapy, which includes a program of shoulder girdle strengthening, is important to avoid recurrent instability episodes of subluxation and/or dislocation. You can try to do it on your own, but ideally you should see a trained health care professional if you want to achieve optimum results.
Good idea. In younger patients, recurrent dislocations are common. Strengthening the muscles around the shoulder may help prevent recurrent dislocation. Surgery may also be required.