My envelope came with a stamp. I can't remember if I had to affix it or if it was already done but there was definitely a stamp with sufficient postage. I remember it was green. :-D You're right about the return address being the same as the mailing address, though. Not a bad idea in case...
DVD-18s, especially from Universal, have always been problematic for me. It's not actually a problem with the pressing or the color format or anything other than the way DVD-18s are put together, apparently. It doesn't really have much to do with your player, either. Some players are more...
I've sent a few things to Universal for replacement in the past (E.T., Hitchcock) and have always received them back quickly. The turnaround is probably around two weeks, if that. They've always been shipped back Fedex -- standard USPS from me to them. I last sent something back to them in...