280z/300zx

So some ******* threw a rock at my car last night while I was visiting my mother in Ca; usually my car is in the garage when at home. Anyway, looks like a tennis ball size hole over the right reverse light. Looking at courtesy nissan I was wondering if I should just get the lense or the whole assembly as they are basically the same price. Not very familiar with tail light assemblies as this is the first one I've had busted. Part number for the lense is 26554 and for the assemply its 26550. Or maybe I'm reading the schematic wrong that they have posted on the site. Could someone help direct me on what part or parts I will need so I know what this will cost me?

Also how hard is it to swap the assembly or lens myself? I'd hate to have to pay even more out of pocket for installation if I can do it myself. It's currently 11pm so too dark for me to check now, plus I'm not home where I have my tools. Thanks