I bought a REPO
 

Well, I'm pretty sure it's a repo. That's how the guys advertised it.
Just yesterday, I bought a 2006 F250 crew cab, 8' bed, diesel with 100K miles.
Of course, it came with a key and the code for the keyless entry system, but no key fob thingys. I'm wondering if I should consider "changing the locks" since it's a repo. Any ideas how much that would cost? Can I do it myself?

Any thoughts?

I bought a key fob for my Mustang online for $19 and programmed it myself. The Ford fobs for the trucks (no trunk button) are all the same, except for a few of the new models. Do a Google search.

My 2005 SCREW is a repo as well. I got two keyless entry fobs with the truck, but none for the remote starter. I bought the remote starter fob on ebay for less than $20, and saw many of the keyless entry ones on there for way less.

Programming these things yourself is very easy. It should be detailed in the owners manual.

Thanks for suggestions. I wasn't sure if the key fobs were a dealer-only kind of thing.

I am also wondering what people think about rolling a repo. Should I be worried that someone will want their truck back? I assume the repo folks don't do anything about/with keys.

I doubt you have to worry about that too much. My truck came from New Hampshire, and I live in CT, so it was a little bit different, but I would doubt you need to worry about the past owner identifying the truck and trying to take it back. There are a lot of F150's out there, so the chances of him seeing and identifying yours are pretty slim...and even slimmer are the chances of him actually doing something to it.