Do some more diagnosis and checking before you get into any tranny work. Vibrations can come from a lot of things especially if you have that many suspension related issues. Check the entire driveline for carrier bearings, u-joints, driveshaft, transfer case, bushings, motor mounts yadda yadda. Most are simple = cheap checks before you pull a tranny and 98,000 k isnt that much mileage even for an abused tranny as the clutch takes most of the abuse.
A vibration that tracks engine RPM's is going to be caused by something forward of the tranny input shaft. A vibration that tracks the car's speed is going to be something from the tranny backwards to the wheels. Options include driveshaft (of course), tires out of balance, bent wheels, a misfire, pinion out of balance, out of balance flywheel, missing bolt in the flywheel, etc.