Can I paint each piece before installation, or should I install first and paint as a complete kit?

You can do either. Painting pieces separately before installation gives you better masking control and easier handling. If you prefer to install first, you'll need to tape and mask adjacent panels carefully. Most builders paint off-car for cleaner results.

What prep work does the FRP need before painting?

Sand the entire surface with appropriate grit to remove the mold release and create tooth for paint adhesion. Wipe down thoroughly with a clean cloth to remove dust. The raw FRP condition means the gelcoat is already sanded — follow your paint system's surface prep guidelines from there.

Do I need seam tape or gap filler between the panels and factory body lines?

Gaps depend on your vehicle's condition and how carefully you align each piece. Modern flexible sealing tape or automotive caulk works well for any minor gaps after installation. Prep your mounting surfaces clean and level before bolting panels down to minimize gap variation.