Actually the taillights of the (European) W124 were changed in 1993...when the W124 became the E-class with the changed hood and integrated grill.

There is no easier mod as changing the taillight lenses and as Ashman wrote, you don't need to change the inner parts of the taillights (although MB will say that you do have to change that).
I changed the complete taillight units of my 1993 300CE, but that is just me...

good luck & greetingz,

__________________
1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)