Do not use osCommerce. If you do then you WILL need a PHP programmer to make some changes or installs.

Use Zen Cart or CRE Loaded (CRE Loaded is also my fav for the reasons noted above) as they already have much of the installs included. Most owners unless they need something special or want to make changes and have someone correct them (since no one likes to save their PHP files first) do not need a dedicated PHP guy/gal. If you want additional support (as most hosting firms do not offer any) Chain Reaction Web is the best place to go for hosting (i dont work there or get paid by them) for CRE Loaded sites, because their team works on or has experience with the CRE project. Sal helps manage both CRW and CRE....which i am sure is a lot to juggle but he does a great job.

Another great platform is Virtuemart. It is for those wanting a more CMS with cart.....i have not run a store on it but from what i have seen it seems to work great.

oh..and for off the rack cre designs go to Template Monster or Algozone as they both have a large selection of CRE loaded options (i dont work there or get paid by them...i have just helped other clients go there and they have been happy) or other firms can design a custom built template for CRE ...such as Inventory Source (i do work there and get paid by them ;-)....but any designer can make your template)