I would change the clutch for sure. The whole kit is under $100.

Doing the axle seals is really easy. Since you can't do them without removing the axles, this is the perfect time. They're about $9 a peice. Cheap insurance.

If the donor tranny has high miles, maybe replace the clutch fork and pivot.

If you want to eliminate any chance of trouble, replace your master and slave cylinders. You can get by with just the slave if the master's not leaking, but it's best to do both at the same time. Slave=$25 Master=$80.

Oh crap. You're auto. Forget everything I said except the part about axle seals. You're going to need to flush/fill that thing a few times, and also your coolant. Buy a gallon of antifreeze, a $6 thermostat (since you'll drain the coolant it's easy to replace), and a case of ATF.

 

I weighed my 5speed and it was 80lbs. Still not super heavy. I used a small bottle jack under the motor (maybe you could use a cut off 2x4 with a block under the oil pan?) and used my big floor jack to lower the tranny and pull it out. You could also lower it to the ground and have a large piece of cardboard under it to slide it out easy.