Resizing it will not work because it is already AT the pixel dimension that he wants it at. Exporting as a PDF for use as a banner on the web? Needs to stay a JPG I'm sure. I know you're done, Charles, but just to answer this for others, you just want to adjust the JPG compression level. It's the window that pops up when you save a file as a JPG in Photoshop. Quality will drop the more you compress it, but so will filesize. Some images respond better than others. Simply moving that compression level around will sometimes make a huge difference.
Charles, there is also a "Save for Web" feature that REALLY lets you tweak the settings, and save them for future use. If you find yourself dealing with a lot of eBay photos, it would be in your best interest to read up on that particular feature and give it a shot -- no more filesize headaches, and no more crappy looking images because you had to compress them too much.
Later,