Engine replacement cost?

I have a 93 4runner with 155,000 miles on it....auto, V6...It's having some issues when I accelerate and the mechanic says that it's "burning oil on the spark plugs" and that the plugs keep charring out. He recommends getting a new engine.....what should I expect to pay for a rebuilt one? Thanks!

Might just be valve seals. Do you see smoke out the exhaust? All the time or only when you cold start?

no smoke...just choppy when idling and when slowly accelerating. .

'mechanic says that it's "burning oil on the spark plugs" and that the plugs keep charring out'

This is what he says?

Are there excessive carbon deposits on the plugs or could it be you are leaking oil? Have you seen the plugs? How many miles do they take to start causing problems?