I would echo the recommendation to buy a good reloading manual or even two. If you have a certain bullet in mind that you want to load (Hornady, Nosler, etc.) I would buy that brand's manual.

I also think you are on the right track about getting a single stage. It sounds like you are going to be loading ammo for hunting, not plinking (if you plink with your 300 win mag you are tougher than me!) so you will be better served going slow and taking your time, rather than just pumping out ammo.

As for particular brands I have the Hornady Lock n Load single stage press with the quick change bushings and I really like it. But you should be well served with any of the major brands. Good luck!