You don't really need to set up a MemPak if you use Jabo's Directinput. Just choose Memory Pak from the drop-down box in the configuration dialog.
If you get N-Rage's Input plugin working, setting up a Mem Pak isn't hard. Just pick the Controller Pka tab and choose Mem Pak from the drop-swon menu and check RawData. if you down't have any MemPak files available, create a new one by clickining on the right button.
I really don't want to sound like a broken record here, but neither one of the input plugins (Jabo's or N-Rage's) is particularly hard to figure out if you just devote a little time to go through the configuration windows and the different tabs. The only things that might sound odd in N-Rage's Input plugin are the RawData option and modifier usage, but if you just want to set up your controls and use different Controller Paks you don't need to bother yourself with those options in the first place, IMO.
EDIT: I suck at spelling today.