I know you want a Remmy, but if you want to do the work yourself, you will want to get a Savage or a Stevens rifle. Both have a barrel nut that with a few hand tools you can screw a barrel on and set head space on your own. With a Remington, you will need to either get it made to accept a barrel nut to set the head space by yourself, or you will need to have a smith cut and time the threads so that you have correct head space from the bolt face. That is why I am a Savage/Stevens fan. It is much easier to build on. Any time you get a magnum, it is good to get the long action (I know, I know, there are short mags). The reason being even with the short mags, if you chose to shoot the longer high ballistic coefficient bullets and have a long throat cut, it can be a problem trying to get a short action magazine to accept and feed the longer dimensions. Now I know there are some options to extend the magazine on a short action, but the long action doesn't require this upgrade.
As for the Creedmore, from my understanding, the short action will work fine with all bullets. This is the caliber I believe I will build in my next rifle if I decide not to go with the Lapua. My cousin has a 6.5 Lapua and anxious to see how it shoots today.