Not much to loose with a junk yard compressor on the cheap, in which case, I wouldn't replace the drier. Now if it's a fairly inexpensive drier, it's good insurance even with or because of going with a used compressor.
New or rebuilt compressor? You'd be a fool not to replace, purge and vacuum the system according to industry standards in that case.
...all that money only to find the evap drain is plugged, then your screwed anyway which way you go.
