It’s on the near side of the fuel tank, you have to remove the water sensor first and catch any fuel, be careful as there are plastic bits can break easily.
There is a version of the Saab workshop manual on line but it takes a bit of navigating to find the right info, especially for the 9-3x.
https://saabwisonline.com/b8/9-3/2011/8-body/body-8-body/auxiliaries/adjustment-replacement-auxiliaries/wing-moulding-front-9-3x/to-remove-703/The link is for removing the plastic wheel arch trim on the front but it took me about an hour to find it so I’m not navigating off the page to look for the fuel filter instructions!
I think you BIL might be the 2nd person here to own a Ttid 9-3x
