How to downgrade from OSX 10.8.5 to Snow Leopard, on an Early 2011 MacBook Pro, without the original installer disk?

Hello! So here are the specs.

I have an Early 2011 MacBook Pro, which came with OSX 10.6.6 by default.

I've lost my installer disk so I though I'd buy a retail one from the online Apple Store, and version 10.6.3 is what they sent me.

Simply running the install OSX app won't work, I get a msg saying:

-- You can't use this version of the application "Install Mac OS X" with this version of OS X. You have "Install Mac OS X" 23.1.1. --

So, I've tried booting from the new disk hoping to erase my current drive and install Snow Leopard, but no can do, I get 3 beeps and have to force shutdown (not RAM related, see below). Laptop works fine when I spare it this maneuver.

After some research I understand 2 things:

1. Only the original installer disk will let me restore factory settings (and I don't have it).

2. I can only install the default OSX (10.6.6) or a later version (that 10.6.3 DVD may not have the correct drivers for my system).

Are these conclusions right? If so, would the Apple Store replace my disk for an updated 10.6.6. one? If not, then what are my options?

Thank you!

References:

http://manuals.info.apple.com/MANUALS/1000/MA1172/en_US/Snow_Leopard_Installatio n_Instructions.pdf

http://support.apple.com/kb/HT3910

http://support.apple.com/kb/ht2186

https://discussions.apple.com/thread/4258610?answerId=19444837022#19444837022

https://discussions.apple.com/thread/3864915

http://forums.macrumors.com/showthread.php?t=1163160