I'd get a scanner to handle it. Even a cheaply like my Epson Perfection 1250 comes with attachments to scan negatives.

If you are on Linux, take care with the scanner you choose. Epson were reputed to be good in supporting SANE (Linux Twain) but my scanner is an oddball, I believe sharing a chip with an HP model. Last time I looked (at least a year ago), there was a driver someone developed for the HP machine that stood a chance of working but nothing specifically for my Epson.

Gimp is a nice tool. Definately worth a look at.