Newbie: Negative Scanning Questions

       I was interested in making digital prints from some of my old 35mm
negatives and am seeking some scanning advice.  My experience with digital
photography so far has only been with making low resolution scans of negatives
for webpages.  My equipment is Adobe Photoshop, a HP ScanJet 4570c with
negative adapter (yes I realize it's not a true negative scanner like the
better Nikon's and Minolta's) and a Cannon i470D bubblejet printer.  I simply
want to make the best occasional family prints I can with this hardware &
software in printing 4x6, 5x7, and 8x10 photos.
The scanner is capable of 2400 dpi and the resolution of the printer is 600x600
in black and 4800x1200 in color.
       1)  My first question involves the scanning format...should I save the
scan as a TIF, compressed TIF, JPEG or GIF?  Perhaps I should save it (archive
it) as a TIF and do the editing of it and saving it as a JPEG to print? (print
the edited JPEG)
       2)  My second question involves the resolution setting of the scanner. 
Keeping in mind that I will be doing 4x6, 5x7, and 8x10 and given that the
maximum resolution of the printer is 4800 x 1200dpi, should I scan the 35mm
negatives at the full 2400 or is that going too far?  The size of the file
isn't really a concern if I can get higher quality prints using the high
scanner resolution.  But, if it the resulting print at 8x10 will look exactly
the same with a smaller scanner resolution, then I'd prefer to use the smaller
setting to reduce computer processing time and space.
       Any thoughts to the above questions are appreciated.  Thanks.