In reply to tom f:
If you're having to ask on here, I have this sneaking suspicion that setting up a payments system for a website is beyond you. Your Dad is probably best off getting a professional to do it for him, who'll be able to do it all right.
If you're dead set on doing it yourself, then this is roughly what I'd do (especially if I had a bit of money to do it with):
* Install a popular CMS such as Drupal
* Buy/find a decent theme for the site (there are themes with integration for things like opencart)
* Install one of the popular modules for a payments system on to the CMS
It is possible to get people who can install/theme popular CMSes for a fairly reasonable fee. They'll also handle all the hosting and the like.