So in my 03 Regal GS the 4T65e-HD the transmission went out of it and I found another one on craigslist from a guy parting out a 1998 Buick Regal GS. Even though I'm already pretty sure I want to be completely sure that it WILL fit forsure. I figured who better to ask than the people on the forum. If anybody knows forsure please comment I could use your advise... along with some advise on removing it as well. I appreciate it.

Will not work as a simple swap. If I remember right, the park gear switch is inside the case on the 03 and outside on the 98. The transmission its self is the same, but the electrical will be different. It can be swapped over, but it is a bit of work.

Is there any way I could use the parts from my current transmission to convert the electrical?

Yes, the case is the same. The valve body and electrical is different. There are a few other small differences inside with the clutches, but you should be able to leave that.

Trans cooler line fittings are threaded vs click style. Not tough to overcome (use a set of 98 Regal cooler lines)

The PNP that Dan mentions is also easy to overcome. You can put an external on and run that way if you'd like. I've done a write up on it. Might be on this site.... found a copy on another site as well
http://www.grandprixforums.net/how-a...ion-49297.html

The other electrical differences, you should be able to repin for and not have to swap the VB. However I've never done this myself.
In theory ...you'd do the reverse of this
http://www.grandprixforums.net/03-tr...9-a-59484.html