Dappeper mentioned the sensors, you will have to replace a couple in the trans, he'd know better than I would about which ones.
It really does depend on what is cheaper/easier and which you prefer. Personally, I can get 01 sensors for the trans much cheaper than a 98-99 PCM, almost 1/3rd the price for the sensors. If I was in your position, i'd put the 01 in and get new sensors.
However, if you can get the proper 98-99 PCM for about the same price as the sensors, or even for a little more, it's worth it just to not have to drop the trans pan and mess with it all.
Its up to what you can get price wise and how much work you want to do, or you can get a tune.
