1. Yes it is a good deal but this is a good week to be greedy. Check the ebay finds section.
2. Personally, I notice very little difference in the key action amongst the various Model Ms. Some believe that the keyboards manufactured by IBM (particularly 1991 or earlier) are better than the subsequent models by Lexmark because the former have detachable cables and denser plastic. The Blue Labels (blue IBM logo) have drainage holes which can actually be useful if you're concerned about spilling drinks near your keyboard. Others like me find them ugly and unnecessary. Keyboard snobs will say IBM > Lexmark brand, White Label > Blue Label. If it is an IBM manufactured keyboard the label will say only IBM and not Lexmark or Unicomp.
Part #1391401 is what most people refer to when they refer to "IBM Model M". Since yours is from 1993, I bet its something else (just check Wiki). Amongst those labels, I doubt there is much difference in plastic density or design.
3. Label should cover it. I'm also overboard and like to the original tape seal of the keyboard inside the foam to make sure it is new. I don't know if you need to do that.
When you factor in ordering a cable and paying a high shipping fee, you'd probably end up spending $80 for a white label 1991 Model M on ebay. On an absolute scale or for keyboard snobs, that's a pretty good deal when considering they can go for $200+ at clickykeyboards. At the same time, in comparison to your $35 deal, it's not that hot. Personally, if you care only about functionality, there's little difference between what you are ordering and the ebay stuff.
