A friend offered to sell me a used Mossberg 500 for $200, only 200 rounds have been fired through it, I know nothing about shotguns and have a few questions. First the safety is stuck in the fire position and from the little research I've done this could be caused from being dirty and can be kind of a pain to fix because the screw that holds the safety switch, question, does anyone have some experience with this sort of problem and how hard is it to fix? Second if it is chambered for 3" can it shoot 2 3/4" shells? Are there other things I should inspect that show wear or neglect. I'm thinking of offering $150 for it, is that a fair price, they only run a little of $300 new. Thanks in advance and happy thanksgiving.