I personally don't trust non-OEM gaskets on our cars. If you can get a Fel-Pro gasket in rubber, that'll be ok, otherwise stick with AC Delco.

FYI, on your oil questions, most of us running Mobil1 change oil on 5000 mile intervals or higher.

ah okay, thanks for clearing that up. yeah i couldn't go to the garage today =( and its snowing, so no work done, but I need an oil change badly, it hasn't been done since I bought the car, but the oil was pretty much new then, but hopefully next weekend I can get some work done. Thanks.

so what exactly would I ask for at the dealer... a rubber gasket for the transmission fluid filter for a 1998 ssei?

Not exactly. You need a transmission pan gasket for your car. When you drop the pan, you will see the filter. The filter is sealed with an o-ring that often remains in the valve body of the trans when you pull the filter out. When that happens, most of us install the new filter using the old ring in place for the seal. They usually do not cause any trouble, but digging around in the valve body can.

Procedure is described in Techinfo

I have a 98 LeSabre and have changed my trans several times due to the TCC lockup valve not working right.

I got a Purolator Trans filter from Pep Boys. Cheaper.
. It comes without a rubber gasket. You reuse the original on the trans.
I agree about not using the rubber or cork that comes with some filters for higher price--reuse the original. I have not had a leak on 93 or this 98 or the 03 I have now. Just retighten slowly and evenly around the pan when you replace. That lets the gasket seal up evenly around the whole pan. I tightened to the 20in/lbs or whatever the book says. That'* about 1-2 ft/lbs on a normal torque wrench. I just noted how much torque it took to loosen the originals and duplicated that when I retightened the final time.

Only problem may be removing the original seal between the filter and the trans body. I used a large screwdriver as a lever to pry the filter down and the to pry out the filter seal. Lube and install original with trans oil or petroleum jelly.