On a 2001 Lincoln LS, the ABS light means that there is a problem with the brake system. The AFS light on means that there is possibly a headlight that is bad or the headlight will not go from low to high beam or vice versa.
if you have a Nakamichi sound system i assume you have a speaker grill before the third brake light by the back window. If so, no problem. Just stick a flat head screwdriver under it and prye it open. Once it opens its easy from there, the difficult part is prying the grill/light open.
Open the trunk and move back the carpet in the interior, there are three bolts that hold the light in place. remove all three and to remove broken bulb twist than pull.watch what your doing if not careful you will crack the light.