Ahh yes, the scanning road is long and windy. Worth the journey though.
A dedicated film scanner, like a Nikon, Minolta, Microtek, etc., will do a better job than the 4990. However, the 4990 should be more than adequate for 8x10s (inches) and for web posting.
To get your negatives to lie flat, go to a framing shop, and get them to cut some anti-reflective glass so that it will fit in your film holders. Lay the film in the film holder channel, then lay the AR glass down on top of the negative, rough side down. This'll keep the negatives nice and flat. Either than, or buy some better holders from betterscanning.com.
Scan at the best resolution your scanner can handle, ignoring input and output sizes. For the 4990, 2400 dpi is about as much as the scanner can really do. Set the output size to "original". Set the sharpening off or to low on the scanner software (the Epson S/W is fine), and set the back and white points on the histogram (see the website referred to below for more info) to avoid losing the shadows and highlights.
Next you'll need to learn how to sharpen. This is another long and winding road! I'd recommend you head over to
The Light's Right, and read up on their sharpening tutorials. Basically you need two to three passes - capture sharpening (immediately post scanning), some creative sharpening (where appropriate) and some output sharpening prior to printing or saving to web. The Light's Right has a whole bunch of other tutorials which I think you'll find useful.
If you PM me your email address, I'll send you a small PDF with some good starter scanning settings.
Another good resource, if you prefer books, is Bruce Fraser's book on sharpening. This takes you from the theory all the way through to runnable actiions.
BTW, the later versions of PSE do support limited 16 bit edits, which are particularly useful for B+W images. Also take a look at PaintShop Pro - it's pretty good value for money.
Good luck!