'94 Jimmy ABS Problems

I have a1994 Jimmy 4x4 and have been having problems with the ABS system for quite a long time now. I switched out the ABS control unit with one from the junkyard awhile ago. My question is, do I need to bleed the unit itself and how do I do that? Is it possible that there is air in the system and that could be causing false ABS codes? I pulled the codes and got back codes 41, 42, 45, 46, 51, 52, 65, and 67. I'm not sure how to diagnose and solve these issues. Does anybody have any tips or suggestions for me? Thanks.

You've taken on a challenge there kchew.
Since 1994 had a mix of OBDI & OBDII parts, a 1994 Factory Service Manual and maybe a dealer scan tool will be required to make it function safely. Even the '92 with OBDI is a little hairy with a factory service manual.
You might check eBay for the manual's (since there was a suppliment manual for '94 also) and scan tool.