In my opinion what matters the most is a good crypter. If the keylogger has the "melt" option it will install and won't be detected that easy. But you need a good crypter for it,and be careful. Almost all crypters posted for free in forums are backdoored (infected).
Read again , OP talks about doing it himself, not using some green glowing skidthingy.
@OP
Python would work just like any other language , the downside to it is that it would be easy to peel down or hard to hide, windows doesnt ship with an interpreter so you would need something like py2exe to make it portable, this is not as pretty as it sounds.
Also a C or assembly program would be much smaller , if you only expose the binary it will be harder to reverse engineer.
Problem is not so much in the logging part its about moving the data in a way that can go undetected, the traditional FTP methods are likely to set off all sorta windows toys.
Anyway there should be plenty of examples , looking at your post it is pretty clear you will have to learn how to code.
Start with something easier and think of the problem in the meanwhile.
You could template it in python , make sure you understand the networking and the OS part of the story, then move up to another language, there are plenty choices.