Oil seal in filter connection (not filter seal)

My daughter's 1996 Isuzu Trooper V6 w/155,000 miles is leaking oil heavily from the oil filter assembly (the oil filter attaches to this unit).

(Not the oil filter or the flat seal that comes with it. have also ensured that an old seal was not left on.)

I am told that there is an "O" ring or seal in this assembly that has been known to go after 120,000+ miles.

Is this true and is this something a Saturday mechanic could tackle or is this a professional only type of job (specialty tools, etc.

Cheers,
David