when doing a motor swap, its not the motor, its the parts that you never think of that will get you to pull your hair out and even question why you are doing this. if your mechanic is doing this, get him a flat rate and not pay him hourly. you might have to get new steering column as the old one is now in the way of the motor. new steering box, as the old one doesn't line up with new motor. not to mention the electronics like getting the dash board to read the new engine. i've had a hand in a few engine swaps and some are easier than others. as cool as it is to think about, something simple like new motor mounts can cause headaches, especially when the oil pan is now hitting the suspension parts.
so think about it, research it, and then double the intended money you are looking to spend.
you didn't say what motor you had. if you have a V6, i would move up to the V8. if you have a V8, i would look more to a more modern one, or something with more power/balls.
also look at your state laws in motorswaps. some will allow them if the motor you put in is newer than the vehicle. some states don't allow the vehicle to be streetable if you have 2 different makes of car and motor. the legality is your first hurdle.