My car came with an incomplete spare tire kit and no key.

If I get a kit from a scrap yard or someplace like that will the key work? I'll obviously be getting one from a 3G TL. If not what is the solution to getting the wheels off?

 

You mean each wheel has a wheel lock right? Each 'key' has a different pattern. The best thing to do is use a cheap socket and bang it it on over the lock. I don't recall what size works but it has to be one that is just undersized to fit over the lock so it spreads slightly. The teeth on the socket should grab the lock enough so that you can use a ratchet to remove

 

I lost the key for my locks one day. I think I left it on the last lock I worked on during a tire rotation.

I drove the vehicle to a dealer and they removed all 4 locks within 10 minutes ( in the quick lube lane). They didn't charge me for the work, but I felt obligated to buy the replacements from them.

You can also buy special sockets to do this yourself. They aren't expensive, but if you don't already have a collection of ratchets and air tools, it's best to go to the dealer or a tire shop.