Shortly after getting my '87, I started having the same trouble, it was almost impossible to shift into R even when sitting still, I pretty much had to SLAM it into R, not a good feeling. Tough to get into 1st from a stop too. I went all through the clutch hydraulics, everything was perfect, and the travel at th slave looked correct. Problem persisted. It ended up being the clutch, it was worn down to the rivets on both sides.
I still have a lot of trouble getting into 1st, but I believe it is in the tranny now, worn out synchros. I typically shift into 3rd, then it will pop right into 1st. Tranny is starting to make a lot of bearing noise, so the end is near. I have a freshly rebuilt R151F in the garage, I just need to install the crawler gears in the t-case, then swap it in.
Lots of noise in every gear but 4th indicates a worn out intermediate shaft bearing. 4th gear is direct drive, 1:1 ratio, no reduction.
Hawkeye, the CEL is not related to the clutch at all, but you should pull the code out of the EFI ECU and see what's up with that.