Will this handle work with the interior door panel already installed?

Yes. The handle mounts from the front side of the door panel, so you don't need to remove interior trim. Unbolt the old handle and bolt the new one in place.

Does this come with fasteners?

Hardware not confirmed in the product specs. Have M6 or M8 bolts on hand (your door panel likely uses one or the other), or check your existing handle before ordering to match fastener size.

Can the chrome be repainted or powder-coated if I want a different finish?

Chrome can be stripped and refinished, but it requires stripping the existing plating first. If you need a different finish long-term, consider anodizing or powder coating after chrome removal—standard spray paint won't stick to chrome without heavy prep.