1. Oil sending unit faulty perhaps?
2. Ad "not working well" means nothing. Can you give more details?
3. Airbag means there is an issue with the airbag system. Could be a sensor, could be wiring, could be one of the bags.
The 2004s are known for many issues, but you have it so plan in tiniest a but more cash to get it running error free.
First things to do is check for any codes at the bod port. This is a GREAT place to to locate issues.
A/c issues can be due too low refrigerant, leaking a/c lines, weak/faulty compressor. If the car was driving in the rust belt the a/c lines that run to the back of the car could be corrodes, causing leaks there. To fix this the car will be to be lifted off the chassis to repair the lines.
Oil could be a number of things, but could be something as simple as a sponsor, the guage in the dash.
If you search the forums you should find some info whilst you wait for responses.