How do I clear my MacBook Pro HD using Disk Utility?

I'm not sure if my MacBook Pro specifications are necessary, so I'll skip those for the time being, but I have a 2009 release which already had OS X 10.6 Snow Leopard on it and came with both the OS X Install DVD and Applications Install DVD for this in case I needed to clear my HD for whatever reason and start over. I skipped Lion and upgraded straight to Mountain Lion when it came out, which I paid for and finally yesterday, I upgraded to Mavericks. This was all through the App Store.

My questions are:

1. Taking into account my situation, would I be best installing Snow Leopard after clearing my HD since I have the DVD for it and then upgrading to either Mountain Lion and then Mavericks, or just straight to Mavericks, or would it be easier to get Mavericks onto a bootable USB and not bother with the Snow Leopard DVD? Keep in mind I'd like the least complicated option, as I haven't done it before. I'm curious because I've read that Mavericks was designed to be used as an upgrade and not so much for clean installs - not sure if that's true or not.

2. Obviously I've got Mountain Lion under "Purchases" in my App Store account and I don't want to have to pay again. If I clear my HD and end up installing Snow Leopard, will it be easy enough to just log in and redownload it without having to pay again? If I do this method and end up with Snow Leopard, will it be advisable to jump straight to Mavericks? The fact Mountain Lion cost around £20 or so (can't remember exactly) and Mavericks is free, I'm not sure I trust jumping...

3. I think I'm ok with actually clearing my HD, but wondering when to insert the disc or USB - will it prompt me or is it just before restarting... Or after restarting? It says on the disc, "To start up from Mac OS X, hold down the C key as the computer starts up'. Confused about the order in which I should do things!

4. In general, is a clean install advisable of just Mavericks? It seems like a huge hassle and I'd rather upgrade from what I bought the MacBook with in the first place. I've read that the recovery partition can go missing if you do a clean install? What is that and does it really happen?

If anyone could help/advise me, that'd be awesome! Thank you! 🙂 PS I'm aware there are a number of different versions of Snow Leopard, Lion, Mountain Lion and so on, so any advice regarding that would also be useful.