I have to agree with everyone else on this.. first, it is good to know that you do have a sense of loyalty, alot of ppl nowadays do not.
However, you also need to think about your career, the rest of your life and your goals. If you expect to meet your goals in life, then it sounds like it is time for you to move on and accomplish those goals; the longer you sit around and do not get to work, the harder it will be on you down the road.
To me it sounds more like it is not so much a "loyalty" thing, but perhaps more that you are worried deep down inside about this type of change since you obviously know it can be life changing; good or bad. In this case, I would cover my eyes a little bit and take the leap!
My advice toward your other employment situation, is to give at min. 2 week notice, in writting, in hopes of them finding someone to replace you when you leave... or give them notice now that this is your plans and that they had better find someone to take your place..so you can train them. And then give notice once again just 2 weeks before your final day.