You definitely haven't mastered the Beginner's method, otherwise you'd be sub40 with it (at a bare minimum, anyhow). That doesn't really matter though, because if you're wanting to learn a better method, and you understand the beginner's method, there's no point in getting faster with your current method if you plan to discard it.
You can ultimately learn CFOP (Fridrich) F2L + LL at the same time (since they're so different). If I were you though, I'd learn them separately unless you really want to bust it out. How fast can you currently do the first two layers? If it's 45s+ then you should probably keep doing that to get the hang of it.
Learning the 4 Look Last Layer is very easy to accomplish. You can do it with as few as 3 algorithms if you want, but I suggest learning the whole bit of 4LLL.
To make things easier for you:
http://fatboy.geekside.com/cube/SunePathway.gif
That will tell you how to solve OLL once you get all edges oriented. Use the Sune algorithm (what you currently use for edge permutation) to go through those shapes. At maximum, you have to do Sune 3x. If you learn Anti Sune, then you can do all OCLLs (Orient Corners of the Last Layer) in 2 algorithms (Sune + Sune or Anti Sune). You can either stick with remembering the Sune/Anti Sune combination, or you can learn all 7 OCLLs (all the cases have algorithms that can be done sub1, so it's worth it to learn all 7).
2 Look PLL is rather easy as well. I suggest learning the A PLL for adjacent swap CPLL (Corner Permutation of Last Layer), some peopel have suggested T and J as well (but that's not necessary for 2 Look). You can learn E or Y for learning the opposite swap CPLL. E can be really fast but it takes a bit to bet accustomed to the associated finger tricks (and might be difficult with a stiff cube). Obviously you should learn all 4 EPLLs (Ua, Ub, H, Z). Either of the U perms can solve all four EPLL cases but it would require repetition.
While learning all of those algorithms, you can be teaching yourself F2L as well, since the last layer is basically pattern recognition and recall, F2L is different enough to not interfere.