1998 Buick Riviera Engine problems

It started out as a small oil leak, but I recently noticed the leak has expanded significantly. It's difficult to pinpoint the leak, but an oil pan under the car shows significant puddling of oil. A sealer/conditioner doesn't appear to have been affected. While online, I noted that the 3800cc 3.8L engine seems notorious for this problem, and other models of gm cars appear to be subject to a recall. Not so the buick, which to me, has the same engine. Given that is is known now, I'm concerned that this low production vehicle was left out of the recall and should be included. Puddle of oil photo enclosed. This condition is most noticeable while the vehicle is stationary.

Tl* the contact owns a 1998 buick riviera. While entering the vehicle, the contact noticed engine oil on the ground under the vehicle. The vehicle was taken to the dealer where it was diagnosed that the valve cover gasket failed and needed to be replaced. The vehicle was repaired. The vin was not included in nhtsa campaign number: 15v701000 (engine and engine cooling). The manufacturer was made aware of the failure. The failure mileage was 56,513. Updated 04/29/16*lj *tr

Tl* the contact owns a 1998 buick riviera. While stopped, the contact noticed smoke coming from the engine compartment of the vehicle. The failure recurred on numerous occasions. The contact was a certified mechanic who diagnosed that the valve cover gasket needed to be replaced. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was 170,000. Updated 04/07/16*lj *js

Tl* the contact owns a 1998 buick riviera. While the vehicle was parked, there was a puddle of oil dripping near the engine area. The vehicle was not diagnosed or repaired. The manufacturer was notified of the failure. The approximate failure mileage was 300,000.