02ram1500,rear rotor. should new one slide right back on? spring system?

Answer 1

Rotor, or brake drum?

If it's drum, you need to back off the brake shoes with the screw type adjuster in between the bottom of the two brake shoes.

Answer 2

Unless they have created something that I do not know about, you still have to remove the dust cap. You should be able to take a chisel or screwdriver and tap it off. behind that should be a nut with a retaining ring. Straighten out one of the ears and remove the nut. After that the rotor and hub should come right off. hope this helps