Need advice on replacing or adding an SSD on a Macbook pro

Hey guys,

I have the (early 2011) 13' Macbook Pro 2.3 GHz. It currently has a 320gb hardrive. I am currently running Mountain Lion on it and it's great, but I've always wanted to add an SSD and replace my optical drive with it. I have a few questions.

1) Can I add an SSD in place of my optical drive while keeping my original hardrive.

2) If I do what I stated in (1), how can I put Mountain Lion on the SDD and if I can, do I have to reinstall everything?

3) Can Apple do this for me?

4) Is it worth it?

Thanks guys!