In my experience which isn't a whole lot the bass rest on your belly. I rest the edge where the back meets the upper bout on my stomach. Ideally you should be able to keep the bass balanced in this position with no hands at all. Leaving them free to play the instrument rather than support it.
The end pin is adjustable (usually) so it can be adjusted for people of various heights. I'm more or less your height so I don't have it out very far.
If you got a lesson or even if you knew someone who played who could show you one or two things I think that put a lot of what your thinking about to rest.
Also do as much research here a you can first before you jump into anything. Look at the FAQ do searches on questions you might have, there's a lot of information to be found here.
If it all possible try and get someone who knows to check out some basses with you it would help a lot.
I didn't have such a luxury but I still managed okay. The guy I bought from was a decent guy which helped a lot.
http://www.amazon.com/gp/reader/0967...33#reader-link
This link is a bit of rufus reids book. Showing how he holds the bass. He has the bass set a little lower than I do. The nut is closer to my hair line.