AMSOIL actually calls theirs Slip Lock. As far as chnageing over to AMSOIL at the first oil change, it doesn't hurt the engine at all. The only thing is that it may take a little longer for the engine to wear in better. I did mine at @6500 miles but then I went across country pulling a TT There has been a study that has proven that most engines aren't going to BREAK in that much more after they initially run them anyway. Most manufactures run themreal hard at the factory which will seat the rings which is the whole purpose of breaking them in other than us towing with this engine. The whole breakin thing is mainly for the tranny and gears anyway.
You may want to pickup some of the AMSOIL foam filter cleaner and foam filter oil t reoil your drop in air filter. What I did was to purchase a second air filter that way one can dry while theother is in the truck
Good luck with getting the filters you need and that was good that contacted the privious owner to get the real goods o the truck