NEX Macro capabilities

Hello all guys and gals at dpreview. I'm new here and new to photographing too.
I got the NEX-5N as my first "better" camera.
I have 16mm pancake as well as 18-55mm lenses for it.

I'd love to be able to get some really close up macro shots but I'm quite tight on the budget. What would be the cheapest way to archive some macro shots?

I see that there are these $8 macro extension tubes available, but can I even use the manual focus of the 16mm or 18-55mm once I attach those?

I also found out that there's this extension tube that allows auto focusing too, it's quite pricey though.

http://www.ebay.com/sch/i.html?_nkw=auto+extension+tube+sony+nex&_sacat=0&_odkw=automatic+extension+tube+sony+nex&_fspt=1&_sop=12&_osacat=0&_mPrRngCbx=1

As for adapters and using some other mount lenses... I have no idea what to look for.

Could you guys help me out a bit here and recommend me a cheap and good way to get into macro photographing.

Cheers