Best way to get at it will be through the passengerside wheel well. Jack and remove the tire. Remove the splash shield and it'll be right there.
It'* held on with 4 13mm bolts. They are a pain in the neck to get at with the axle in place. Pull the oil pressure sender out first. Using channel locks and only squeezing the metal, not plastic body of the sensor.
If you are thinking about doing a transmission service (drop pan, change filter, refill) then I'd do it at the same time and pull the axle. Doing so gives you all the room you'd ever need/want. It'* possible to do it with the axle in though.
I found using a razor blade in small vice grips or a small scraper worked well. Then spray a cloth with brake cleaner and wipe, don't spray anything directly into the area with it open.
00 Regal GS: All kinds of cool stuff.