New Owner/ Keyless?

Yes.

(Factory, port, dealer installed.)

Check your owner's manual, available online if you don't have the paper.

So, if I understand correctly, any 97 avalon should be able to have a fob added to it by simply programming it?

Only if the Keyless system was installed at the factory or dealer. It was an option. The OM will tell you something is optional by using the word "some".

On my '99 XL, the dealer installed receiver is under the front pass. seat.

Amazingly enough, as the third owner of this car, I still have the dealer window sticker. No keyless listed

Anyone know where the receiver would be located? Under each front seat is an unused connector fed by 2 wires each. I'd assume this is for the butt warmers (which I don't have, and will likely miss come February)

OM says "Your vehicle has a wireless remote control system that can lock or unlock all the doors or open the trunk lid"

The receiver is in the trunk on the left side near the fuel filler tube(best way I can describe it)

I've got a pretty orange wiring harness connector there, but no magic box

Which leads me to my next question.. where can I find one cheap?

ebay! or any aftermarket kit

Found a whole heck of a lot of fobs, but receivers seem to get lost in the noise.

aftermarket

the car has power locks right? I would just go with an aftermarket kit you will get better range and more features.