I know of a 1985 Celica ST coupe, the body is really clean, no rust, 100,XXX miles, 5 speed, but blown head gasket. I can get a used engine that has 155,XXX miles for around $300, SO what I want to know is how hard is it to swap out the motor? and is it worth it?

Can't you just replace the head gasket? or has the engine been trashed?

Can't you just replace the head gasket? or has the engine been trashed?
No the head is warped, and coolant/water have been sitting on the pistons... so they might be pitted.