I have noticed my 4th gear shift kinda thumps. It done that before the rebuild and still does it after. I have a DHP as well, but it is a 98 PCM in a 98 car, I dont think the fact of it being a different year would have anything to do with it in your case. I have an Overkill PCM on the way, so I will get to see if there is any improvement.
The fourth gear clutch set and chain is accessible with out pulling the tranny, but you have to get to the side cover and there are several things you will need to remove. It is not a job for anyone that does not have some decent mechanical skills.