I need to create a web gallery for a photographer that wants to automate the process of uploading lots of images to a web gallery (thubnails and watermarked if possible) so that clients can then dowload a required image using something like paypals payloadz function!

I come from a design background so have basic knowledge of Dreamweaver ect but not much programming knowledge.
I need advice on the simplest way to go about this. What do I need, do I need a database (what in), do I need PHP or some other code, is there a plug in app that can speed this up???

Any advice or help pointing me in the right direction would be greatly appreciated.

D