I am assuming you have the stamped rockers that are stock which are SA. If you know that for fact than yes remove the guide plates. IDK if the shop that did the work put on NSA stamped rockers.....which would explain the guide plates if that is the case
or install FULL RR that are NSA and keep the guide plates
You can change the valve stem seals without hooking air up to each cyl. This way the valve just drops about 1/4-1/2".
rotate motor to #1 TDC and do cyl 1 & 6
rotate motor 90 degrees and do cyl 5 & 8
rotate motor 90 degrees and do cyl 7 & 4
rotate motor 90 degrees and do cyl 3 & 2
Since you need to take the valve springs off to do this...replace springs if they are still the stock ones