Customization of VirtueMart for Joomla. Small job

This is a re-post of the project I posted yesterday, as I made a mistake with the budget. This is a very small job, so it should be very low in the price range for this project. I need some customization done on tax settings before and after login on a shopping site. Please explain to me what your experience is with Joomla, VirtueMart and customization of them. Bids with just a remark "I can do it" without any explanation will be ignored. I will only give more information to people who can explain to me that they know what they are doing.