Inspect any low-hour 302's you find with a fine-tooth comb to convince yourself that the hour reading is true. If a certain board in these machines goes bad, the replacement board which also has the hourmeter on it will restart hours at zero. This straight from a Miller tech when I called him about a 302 I was looking at and the hours didn't match the machine's appearance. If the board was replaced under warranty, Miller will have a record, and likely the hour reading(s) at replacement(s) ... if replaced after warranty they won't have records at all.
I would also suggest you call Miller with the S/N and let them tell you any warranty repair history and verify it isn't stolen.