In my humble opinion -- definitely REPLACE. Hopefully the oil pick-up isn't busted off or damaged. Highly recommend installing oil pan guard (http://www.fiatspider.com/f08/viewtopic.php?f=3&t=21991) after getting the oil pan replaced.

Shouldn't be too bad a of a job. Not fun. Just tedious and messy. Much easier if you have a lift rather than just jack stands. You'll get a chance to inspect the bottom end while the pan is off. Hopefully you won't find any surprises as the rest of the car looks to be in fairly good shape.

Repair, unless its too bad or you find an original pan in good condition. The newer/re manufactured pans available don't have the baffling to control the oil sloshing around. Besides that, the new pans are expensive.

it kind of a big job however it needs to come off and one needs to go on
its not rusty so it will bang out just fine
place the pan on a board and get a 2x4 set the 2x4 on the dent inside and hit it with the biggest hammer you can get
you'll need a gasket and some help from someone who knows a bit about cars and a engine hoist
many people like these cars enuff it help for free

best of luck to ya.joe