I'm sorry no one has answered your post for so long. I just became a moderator here and found it by looking for posts with (0) responses. I like the way you are thinking about approaching this and it sounds like you are on the right track. It also sounds like you are not afraid to jump in and figure things out. That's sort of the best way to approach 3d printing. I think that you might want to get started by buying an inexpensive printer that you assemble yourself and just dive in. You'll learn about slicing by doing it. Once you pick up a few key words or phrases you'll have better words to use to do searches using them and you'll find lots of answers. I started the same way last year and have had very little trouble finding answers to what I needed.

I assume that what you mean by "printing fully assembled products" is that you want to print products that have multiple parts and or moving parts all in 3d and then fit them together to have something useful or working. It's difficult to print a single object that has moving parts but prints in one pass or session. You'll have to print parts separately and then put them together for the most part. And there are a few limitations. One side of the part has to stick to a bed that is moving to be able to print. So, there is always a flat side. That creates design challenges and there are creative ways around it but it's a hurdle sometimes.

It's difficult to teach someone to think spatially. Either you have it or you don't. If you can see it in your head, then you have a start. You now have to get it out of your head and onto paper or into a model on your computer. Do you sketch or draw? That's great way to start. Sketch your ideas and they don't have to be pretty. They just have to be good enough so that you know what you are thinking. Then get something like Blender and start modeling. It's a free 3d software at http://www.blender.org/. Or go here for software: http://www.shapeways.com/creator/tools.

You seem to be a self-starter. You are asking where to find good places to get you started I think the answer is that until you jump in with both feet, you won't necessarily find them. Once you have a printer in front of you and you print your first cube, you'll be amazed at how fast you figure it out. Then come back here and post in one of the other forum sections where people are getting printing help. This section is sort of off the radar for people with printers and printer related issues. Once you are up and running there are many people who will go out of their way to assist you.