Other Fuel System Tank Filling/charging problems of the 2002 Buick Rendezvous

Noticed smell of gas by the 2002 Buick Rendezvous. Mechanic verified there was a leak near filling point of car. Said would be expensive to fix this, thought he saw something about gm recalling gas tanks on some vehicles. Looked it up and saw many complaints about this issue and there was a recall. This was my parents car, now being used by my teenage son, so I looked in their file and found a letter sent from gm that a crack could occur in the tank due to a defective product and if it happened to the vehicle they would replace it. Wrong. Apparently a dangerous fire hazard doesn't matter after 10 years. Gm said this replacement offer has expired. Gm told me to make an appointment at a Buick dealer to have them verify the problem. The dealer I brought it to told me not to waste my money having it diagnosed by them, since my mechanic had already verified it was leaking in the defective spot, because gm never covers this previously offered repair anymore. The 2002 Rendezvous has only approximately 45,000 miles on it!! owned by my parents who took meticulous care of it. What was supposed to be a great car for my 16 year old son is now a fire hazard, and essentially unsellable if I have any conscience!! I cannot believe gm refuses to uphold their promise to repair this completely, dangerously unsafe defect, that they allotted replacement parts and money for, because they knew it was their defective part they put into these Rendezvous. I guess they are waiting for someone to actually blow up to put this repair back into place.