Im replacing my Ferrari 328 15" replica wheels to upgrade to larger more modern wheels and tires. They are in good condition. What are they worth with tires?

Not worth much really if you want good money you need to be the one refurbishing them as nobody wants scratched wheels.
The one buying them won't be just bolting them on he is trying to build a Ferrari too so will want them perfect.

Which bolt pattern; Fiero 5x100 or F*car 5x108 ?

5x100

All stock Fieros are 5x100, even with body kits like Mera, unless owner has changed hubs and axles.