My 98 Explorer SOHC A/C stopped working late last summer and the dealer
indicated that the accumulator (drier) was seeping and had some rust issues
(blend door is OK).  They recommended replacing it and the pressure cycling
switch but wanted over $500.  I decided to wait till after winter and did
some research and discovered the accumulator is pretty easy to replace so I
may try to do it myself.

My questions are:

1) Since the AC is completely warm, even on max AC do I need to worry about
taking it somewhere to recover the R-134?  I wouldn't think there is any
R-134 in the system to hurt the environment anyway as the AC does not cool
at all.
2) How do you discharge the system?  Do you need to disconnect the
compressor somehow and run the truck for a few days?  Or do you simply use
the Schrader valve on the low side (same port that you add R-134) and let it
out?
3) Anyone know how much R-134 is need to re-fill after a complete discharge?
4) What would cause rust in the accumulator anyway?  I though the system was
full of refrigerant oil to prevent that.

My basic plan is to replace the accumulator myself and then take it
somewhere to get the system leak-tested and recharged.