I did the same thing on my old '92 318. I water sanded it then used Scratch X to remove the scracthes and polish the lens. It looked good but I remember Meguires sells some special stuff specifically made for polishing plastic.
Hey Dave, what kind of polish did you use?
'02 C32 AMG @ 18psi - Eurocharged custom ECU/TCU, ASP 178mm crank pulley + NW PSK, CM30 i/c pump, NW i/c iso kit, EC i/c, Magnecore wires, NW CAI, SL55 Y pipe, NW ported intake manifolds + gaskets/spacers, NW inconel exhaust manifolds, NW catch can, dual exhaust, H&R sways, H&R coilovers, H&R spacers, Quaife ATB LSD, goodridge lines, EBC yellowstuff, AMG 18" rims, Zeitronix datalogger.