- Install the bitcoin client on your server for create a wallet and run the daemon for make transactions.
- Deal with Mt.Gox API (curl only with PHP, json_decode don't work) for check the current price of last trade in dollars. For example, make a CRON that will check the price and convert all prices on the website or stock the current price and convert in live products prices.
- For payments, give an new payment address for each transaction and wait the customer pay by check how many bitcoins sent to new address and at least 1 confirmation (average, 10 minutes).
I do almost the same thing for my gambling website. Good luck!
I think this is how I'll go about it, but it's probably better to use bitcoin chart's numbers than MTGox, right? Maybe both for a sanity check.