If your after a free e-commerce website, then OSCommerce is one option. Its PHP based, its a nightmare to work with (imo), but its free and used all over the net (a big giveaway that a site is based on it is the /acatalog link that you see when browsing - OCUK used to use it until they upgraded).
You don't need decent HTML skills to use the default templates with it, but they do help, and you will need to know some PHP.
Looking down the (imo vastly superior) .NET route you have something like DotNetNuke, which has numerous e-commerce modules available for it. Take a look at www.dotnetnuke.com for some more information about dnn, but as with OSCommerce this does again require some programming knowledge..although its C# you would have to learn rather than PHP.
These are both pretty much off the shelf products that neeed a little modification to make them work as you like, so may not be suitable for you. There may be a much simpler way though.
He doesn't need a proper online shop from what you have said - so it may be a simple case of putting up a single page website which has an "email me" link, and then he can setup a paypal account and use that to recieve payments and order information. That should be very easy to do, and requires no scripting or server sidecode at all - just a simple xHTML webpage with a mailto link 
Something as simple as this - i've not done any CSS for it but have spent a few seconds showing you the type of thing I mean.
Code:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<title>Welcome to Car Parts LTD</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
</head>
<body>
<div>
<div class="Title">
<h3>Welcome to Car Parts LTD!</h3>
</div>
<br /><br />
<div class="bodyText">
Put a bunch of text here, and maybe some images
</div>
<br /><br /><br />
</div>
<div>
Click <a href="mailto:your@email.com" title="Email Us!">here</a> to email us with your requirements, and we'll get back to you asap!
</div>
<br /><br /><br /><br />
<div class="footer">
Car Parts LTD is registered in England and Wales, company number 1234567
</div>
</body>
</html>