Niehoff, purchased it from Murray'* Auto Parts for around $25. And I don't know if they will take it back if I buy one online and trade them out because my dog chewed on the box while I was under the car

Do they have a difference in shape and size? The new one I got looks just like the old one

OK, I went to Rockauto.com

1998 Pontiac Bonneville SE has this listed:
STANDARD MOTOR PRODUCTS Part # PS246T {TRU-TECH}
WITH GAUGE
http://info.rockauto.com/getimage/ge...ages/PS246.jpg
(Click link above for image)

1998 Buick LeSabre Limited has these listed:
The same as above (PS246T); and,
STANDARD MOTOR PRODUCTS Part # PS270T {TRU-TECH}
WITH LIGHT
http://info.rockauto.com/getimage/ge...ages/PS270.jpg
(Click link above for image)

This tells me three things:
1) Bonneville apparently only comes with gauge (while LeSabre can go either way).
2) If your store looked up your part under 1998 Bonneville, you should have gotten the right one.
3) If yours is the longer-bodied model (see the linked images), you definitely got the right one.

Assuming you got the right one; did the leaking stop? Are you sure you threaded it in all the way? Maybe try some teflon thread sealant (from a tube, not pipe tape)?

EDIT: I see Bill Buttermore already suggested the sealant, and to leave a few threads clean for possible grounding; interestingly, I cannot find any relevant info (wiring diagram, connector endview) about the oil pressure sensor / sender anywhere in my 1998 FSM...GM oversight?...so I cannot tell you whether the sensor grounds through the block or through the harness. If through the block, maybe the threaded hole needs cleaning?

I believe I got the correct one. The guage still reads, but it seems off since it sometimes says at idle that my oil pressure is right above the red line. I'll get some pics...

Start-up



Running

What kind of miles are on your car? It could be that the guage is accurate, you know.