If your finding oil in the depressions by the fuel injectors the Valve Cover gaskets are shot. On my 91 the VC gaskets are like rubber bands that fit in a slot in the lip of the VC.
Do you know anyone that works on cars themselves? Friends, co workers, neighbors, relatives? Ask around to see where they have their cars worked on.
As one poster mentioned it might be wise to drop the oil pan & inspect the pick up screen. As far as I know the pan comes off easy on that model car.
My mom has a 91 Cadillac that moves about 800 - 900 miles a year and the oil is changed once to twice a year. No sludging here even though it doesn't go very far. Mostly short trips of 2 - 6 miles round trip to the store, bowling & the mall. Every now & then I use it to run it about 25 miles or so.
Never had a problem using Penzoil on her car. I use Castrol 5 W 30 on my Buick & 10 W 30 on the Bonneville.
Run a good quality cleaner through the engine. I've used Mystery Marvel Oil throughout the years on my cars. Run the car on the highway for an hour or so & get it really hot - then have the oil changed. The oil change attendant will love that.
Good Luck
harryface
05 Park Avenue 41,000
91 Bonneville 306,670