I have a whirlpool range

Question

i have a whirlpool range that was purchased 04 2000. last week when i would set it to preheat 350 i was smelling gas and the oven was not preheating unless i set it to 500 and then it wasnt getting as hot as it should now today when i set the oven to preheat there is no smell of gas and no heat at all is it worth repairing. is there something i can try before i have pc richards come to do a repair, THEY WILL CHARGE 139.00 PLUS TAX ANd parts