So I need some help here.

Here's what I have.

Mavic Ksyrium SSC.
Giant TCR Team ONCE frame, vert. drop out.

Here's what I want.

Use the frame and wheels.
Option 1 fixed <---- would really love to try riding a fixed gear. I promise i won't wear cut off jeans, t-shirt and a cap, while sipping on a starbucks coffee.
option 2 single speed. (If I go with single speed, that'd be easy, get a tensioner and be done with it)

Here are my questions.

1. Can I convert the Mavics freehub to a fixed gear type without rebuilding the wheel.
2. If #1 can be done. How can I make sure there's no slack in the chain? I can't seem to find any calculators for chain length. Is it possible? I can buy one of those links that allows you to remove or add a single link, instead of 2. That should help right?

Thanks. any help will be appreciated.

I'm sick of riding my commuter around town just to pick up lunch or something. Too scared to ride the roadie 'cause well, San Jose sucks! lots of bike thiefs.