Need help. Is this speedmaster a good deal

I got a talent for over paying for watches. Is this vintage omega speedmaster. A local pawn shop has it for 4k after taxes. No service history. The braclet is an omega bracelet but from a different watch. No box or papers. From what I seen online I could find one for under 5k. It’s from 1979. Would I get burned on this. Also what to expect for servicing cost. Thanks