Do I need to paint each piece separately or as a complete assembly?

Paint each piece individually before installation. This gives you better edge coverage and lets you handle and cure panels without worrying about fitment interference. Mask off mounting surfaces before priming and painting.

What gap filler or seam tape should I use between the pieces?

FRP seams work best with flexible polyurethane sealer or urethane caulk applied after installation. Sand the seam lightly, apply sealer, and finish with sandpaper once cured. Check your local automotive supply for urethane products rated for plastic-to-plastic bonds.

Can I install this myself, or do I need a professional?

DIY installation is achievable with basic hand tools and jack stands. You'll need to drill or remove existing fasteners, align each panel with body lines, and secure with hardware appropriate to your vehicle's attachment points. Reference your vehicle's service manual for fastener locations and torque specs. Take time with alignment — gaps cut installation work in half.