even though you got it theres an easy way to do that on photoshop...
when your saving your pictures it askes you the quality you want it at just set it at a little lower quality and it makes the file size lower and with photoshop the picture will still look fine
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.