If anyone has a guide on how to provide a bitcoin exchange for my webstore or even wants to help me on the project send me a message.
You are describing and exchange but what you are really describing is an online store selling in-game currency and vouchers/codes, correct? (e.g., similar to what this likley competitor of yours does: http://bitcoincodes.com
then click Gametime for pricing ?)
If so, then what you are probably looking for is ecommerce / shopping cart software that supports bitcoin as a payment method. It looks like you've already got a shopping cart functionality on your site. Which software are you using? Perhaps there's a bitcoin module for it?
For instance, for OSCommerce there is a Bitcoin payment module:
There also are merchant solutions from Bit-Pay:
and from Mt. Gox: