All of sudden there's no reverse?

Sorry I haven't got back on this. I've been out of commision
for the last 2 weeks. The trans is in a 1987 short bed4wd pickup. I'll talk to a trans shop & give them all
the suggestions given. A shop had given me an estimate of $1200.00 to fix reverse. I'm debating about getting another trans from the junk yard. Any suggestions on this idea? Thanks