I want to replace the headlight lenses on a 2003 acura tl, how hard is this to do and any info would be appreciated.

 

Do you want to replace them because their foggy/dull or you want something that looks different? Most auto parts stores sell a kit to clear up dull plastic lenses. It's a bunch of different grit sand papers and some polishing compound. cost around 20 bucks and about 2-3 hours of elbow grease. If you get the kit, take your time and sand the hell out of them. put a couple layers of painters tape around the lenses so you don't scratch your paint. It'll make a HUGE improvement. Good luck