Geez Louise glosrfc - that's some tips!!! Thank you.
Not a problem - just trying to explain the enormous filesize as well as what some of the scanning options actually mean. Providing you use the settings at the end of my post you'll have a digital version that should be suitable for retouching.
The only change you might have to make there is the resolution. The rule of thumb is straightforward - scan no more than 300 DPI for print or 100 DPI for screen. The only exception is if you plan on enlarging the final print, in which case you simply multiply the enlargement by the DPI. For example, if you want to create an 12x8 print from your 6x4 original, 12/6 = 2 so your scanned DPI is 2 * 300 = 600.
Incidentally, if you have a DSLR simply taking a new photo of an old image can be more effective than scanning, particularly if the paper is textured. Just make sure the light on the image is even, that the image is flat, and that you're square on to it. Use a tripod, aperture mode, F8, autofocus on the picture, then snap away with the self-timer or a remote.
Anyway, however you digitise the image, it sounds like there are plenty of members willing to have a go at correcting it for you - good luck!