I suggest you start with a practice Library (software manufacturers jump though loops avoiding the word "database") and try several methods of importing and storing your collection before fully committing it to being managed by Aperture. This will allow you to get up to speed, and become comfortable with, Aperture, as well as give you the knowledge you need to wisely structure your Library.
Don't be put off, however: Aperture is great, very well worth learning how to use, and far, far superior to any file-management system.
First, make a complete copy (a back-up) of your entire collection. Store this somewhere safe.
Second, copy a sample of your collection, including many folders representing your current file-folder storage structure, to a new, clearly named Finder folder ("Sample Image File Tree").
Third, learn how Aperture imports files: what happens to the file, what Aperture calls that file after it is imported, etc. Note that you can import files into Aperture while leaving the Originals where they are.
Fourth (this is the tough one) make the conceptual leap to image-management from the flat-land of file management. Here is a springboard. You don't need a parachute: you'll know you have wings when you fully understand the freedom that "Any image can be in any Album, and can be in as many Albums as you want." represents.
It is important to fully and carefully define "photo". In file-management systems, "photo" = file. In image-management systems like Aperture, this one-to-one correspondence no longer exists.
Here is an example of setting up an Aperture Library.
Again, it's a BIG first step, but after that it's an easy and often thrilling walk. Post back with questions as you move forward.