Typically the newer benzes (and some old ones) have a removable inner "bucket" that holds the lamps and reflectors and an outer lens assembly sealed to the body. This is true of the W108 chassis, and is in fact required on all 1985 or so and later cars in the US.
There should be a couple plastic knobs holding the "bucket" to the body on the inside. It's been a while since I pulled mine to check some bulbs, so I don't remember exactly, but it's fairly obvious and easy.
That can be replaced by unplugging the electrical connector.
The lens can be removed by taking the nuts off the bolts that hold it on. Nuts are on the inside, I believe, don't remember how many. Get a new lens to body seal if you remove the lense, it's cheaper than messing about with water in the trunk.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!