If any front end parts are bad at all, including upper and lower ball joints, tie rods, idler arm and pitman arm, you won't be able to stop the uneven tire wear even if they are able to do a good alignment on it. Ball joints really aren't that hard to change out. I suggest doing a front end rebuild before getting the new tires and then an alignment. Do the alignment with the new tires already on the truck.
I got a front end rebuild kit off ebay for about $250 shipped. Even if the parts aren't as high quality as OEM is I needed everything and the kit is still working fine for me and I saved about $400 over OEM. I'm very happy with the fit and quality of the kit.
This is the kit I used:
http://cgi.ebay.com/ebaymotors/Ball-...4798QQtcZphoto