1.
The rolling in first gear with the clutch in is going to be a problem with either the master or slave cylinder. (wont let the clutch fully disengage
ANSWER: It may just need to be bled or fluid added or replaced. If you have the internal style slave cylinder than I would recommend replacing this when you do the clutch no matter what.( they are prone to problems)
2. I would not recommend trying to rebuild the transmission unless you have done it before.
You will need a hydraulic press, gear puller, and also tools to measure shaft play etc.
3. The cross member they are referring to is the skid plate itself.
4. You will need to pull the transmission back about 6 inches before you can drop it out. The Input shaft is what is keeping it up, it slides into the clutch that is attached to the flywheel and your engine. Use a pry bar between the bell housing and engine to separate them or just wiggle it and push. make sure you have it on a jack with wheels that will allow it to just roll back.
Hope this helps!