I've got a new AC compressor headed my way to replace the one in the car, with dead bearings. So The system still cools, but the bearings are locking up and causing bad engine drag. The systemis still fully sealed and worked great last summer.

So I have the new compressor. What else should I do at the same time? Probably the evap can right? How about an expansion valve? Anything else?

The system was swapped to 134a back in the 90's when it was all fairly new.

My advice, drain the oil from your new compressor, all of it, and put in some PAG 100 synthetic oil with the dye in it. Don't take for granted that the oil is R134 compatible, as most if not all compressors sold for the '91 are charged with R12 oils, and they won't be the right viscosity.

Having done my '91 245 last year, do a very thorough system flush with the solvent (get the residue free solvent from an A/C shop, not the crap in the auto parts stores).

When you pull the orifice tube out and it has black crud all over it (which it will) remove all the lines, condenser, accumulator, and flush each part or line separately with compressed air, then replace the seals. Spen extra time flushing the condenser, as this is where most of the black crud will accumulate.

BTW, there is not an expansion valve on your car, there is an orifice tube located in the high pressure line between the condenser and the evaporator, just ahead of where the pressure sensro is located near the lower radiator hose. Break this fitting, extract the tube and clean the line ahead of the tube well.
Also, use the OEM orifice tube, don't get suckered by the 'adjustable' orifice tubes, they are a waste of money. Also get a new schrader valve that goes on the accumulator, they are cheap from NAPA and usually leak in time.

All new seals at every connection.

orifice tube and dryer, if your car is so equipped.