I unplugged my front passenger seat to remove it from my 2006 Altima (FOB Key) and when I replaced it (making sure the wire harness was connected) the air bag lights now are flashing. The lights were not on when I removed the seat, so I am thinking the system needs to be reset.
Is this something only the dealer can do?
Of course, when I called the local dealer they said yes and I would have to bring it in. The cost to run the diagnostics is $140.00. Trying to save some money here.

Hey and welcome to NICO Club!

Check out the FSM for instruction on things like that. One of our most valuable resources. Below is a link to the whole thing. Each link there is to a specific chapter. The SRS chapter is airbag related, look at page 20 for a switch to and from diagnostic mode and try that first. The FWD chapter has the table of contents, so look there for future use.

http://www.nicoclub.com/FSM/Altima/2006/

Let us know how it goes.