Krissy,
If your images are overexposed you could try to change that using the levels function in photoshop, what I usual do is select the overexposed area with the magic wand tool in photoshop then change the brightness with the levels and curves functions.
As for the grain you can run them through Neat Image (
www.neatimage.com) then take the filtered image into photoshop and apply some unsharp masks with the settings
333%
0.3
0
If that dosent work, if its possible to take the photos again (if it wasent taken at some sort of one of event) try using different apperture settings and if you can, exposure compensation, also a lower ISO setting (if you can) to help reduce grain.
Hope this helps
Joe.