Anyone replace a wiper motor???

[Firebirdjones]

I'm looking at this thing (under the dash of all places). Just like to hear some experiences and/or tips.

Were you able to access the linkage nut through the cowl or did you have to remove the cowl cover?

Does anyone know the difference between a 3 prong and a 4 prong wiper motor? I get asked that question at the parts stores. Looking at the harness under the dash, there is only a dual terminal flat spade connector on the wiper motor, if there is another terminal (or 2) it must have a single wire spade connector on it and I just can't see it up there.
I was hoping someone here would know the difference in the wiper motors,,,like maybe it had to do with another option that may or may not be on the truck?? That would be an easier way to tell rather than ripping this thing apart. I'd like to get the right one on order so I can swap it out with minimal down time.
Thanks.