My mothers car is in need of the ATF to be changed but I want to know if the strainer/filter should be changed as well. Going to be using OE fluid, Type T-IV. If the strainer needs to be changed, what material is the OEM pan gasket? I've seen rubber and I've seen "cork", the service manual doesn't say to apply sealant so I imagine it's a cork or similar material from the factory.

Any help would be appreciated.

 

I'd say if the pan gasket is not leaking then don't touch it. The filter should last twice the interval of the fluid change.
More related info: http://www.clubxb.com/forums/showthread.php?t=45298

 

Just did a transmission oil change on my sons Xb at 60K miles, and I don't think it was necessary after doing the change with the filter at 30K. At 30K the filter had hardly any color change at all, perfectly clean. There was a really small amount of black dust covering the metal part of the filter, that would go thru the filter media without being stopped. There was a small amount of stuff on the magnets in the bottom of the pan, but nothing to be concerned about.
At 60K the oil that came out was clear red and smelled just like new.

The filter kit I got at 30k had a rubber gasket, replacing the OEM cork gasket. I used a red permatex spray to hold it in position and torqued the sump bolts by hand. No leaks in 30K miles and At 60, I didn't bother with the filter.

If the car makes it to 120K, I would change the filter again then. I'm going to skip the 90K fluid change, not worth it.