Can I get a shipping label from my local post office (USPS)?
USPS does not provide labels, free or otherwise. If you can't write on the envelope or box and you feel the need to have a label, buy plain white labels and use those. But I can't figure out what your problem is with eBay's labels. You choose which options you want (3 day shipping, economy, etc.) and click when you are done and you paid. The label pops up and you just print it. What's so difficult about that? I've done it numerous times.
No, the po DOES NOT create labels for you. All you have to do is make a plain to and from label in word on ordinary paper, then take it to the po to get postage attached. Or, go into the usps website to create a prepaid label, if you are using flat rate or know the correct amount.