My oil one is broken

What /where is the best approach to get the rust taken off and car sealed /painted?

I just had my oil changed about 2 or 3 weeks ago. I had noticed it was leaking but put it off. I was headed to the store and my truck started idling rough and had no horsepower so i checked and i had no oil what so ever. Later that night i put oil to make it home and when i went back to place who did oil change he told me that its misfiring cause i have oil in my cylinder.

RPM is low it is always below 5, i need to hit the oscillator gas to to start the car most of the time. Other time the engine will die while i am driving i but in natural and step on the gas couple of time to restart the car.

Just want to know front or rear heater core so I can order right part

It's time for tun up or just have to change spark plug s

The engine emits a tapping noise on start up. The noise may dissipate immediately. Someone claim that the oil relief valve is stuck or something. I check the repair manual and found that it has valve on the engine close to the oil filter. The oil filter is new (nissan) also the oil have been changed 5-30.

Maf circuit on idle 1.50 voltage. No change, still smoking.