autozone uses rebuilt distributors. Yep I'd use the warranty.

the O2 heater... if you have a multi meter you can check the heater. With the key off, just make sure there is a low ohm reading (~100ohms or less)between the terminals of the O2 sensor. (the two black wires) With everything cold of course.
If you don't want to crawl around under the hood/car, check A6 (orn/blk) and A25 (yel/blk) at the ECU for the same connections.
With the ignition off there will not be power on the wires, so don't worry about that.