Upgrade Advice Needed: Dual 800 G4 Quicksilver

Specs:
Dual 800mhz G4
1gb RAM
80gig HD
Combo drive
Zip drive
An nVidia Geforce 4mx card 64mb with ADC/vga. (ADC->DVI)
The case looks like its in great shape from pictures.

1) What is the max HD size for this model? I plan to swap the main for 250gb or add a second 80gb.
2) Are they good at accepting generic DVD-R drives?
3) Zip drive: just keep it? or is it worth any $$
4) What are my GPU upgrade options? ADC->DVI Does it give a produce a good picture?
5) Should I get a USB 2.0 PCI card? I have quite a few devices.
6) Must have wireless internet. Was thinking of buying one of these. Anyone have any experience adding wireless to G4s?

Thanks for advice 🙂

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looking for some upgrade advice now as the powermac is on its way!