It looks like the items to collect are actually ghoul fingernails, ghoul teeth and skeleton skull (not ghoul toenails). These items are frequently dropped and can also be sold back to the store (as well as the Search Paper you get when you undertake the quest) for 10 adena each.

The scrollbook can be safely enchanted to +4 and is -2 AC with +1 INT. It's not quite an elven shield, but you'll have to make the decision between an additional -2 AC or +1 INT. (Also, don't forget that it's almost twice as easy to make a +4 item into +5 than it is to make a +6 item to +7.)