Just picked up an old LJ, And just got it running.

A few questions however
1) The Master Cylinder is leaking Oil through the Firewall into the Cab...
Where would I go to get a seal for this car... and what is the best way to go about changing it out?
2) The Rims are they the same as standard sierra rims?
(Offset, Diameter, width etc?)
Or the LJ's have a different Rim... just after a spare for it...
3) Also not sure what model the LJ is....
Only thing I can find on it is the VIN, nothing else to identify the year, or model.
Are there any obvious ways to find out what model it is? Or can it be determined by the VIN?
Thanks in advance
Adam