Take both of the floor mats out of the drivers footwell (Frankly I find this as being the hardest part of the operation)

There is a gray clip on the bottom of the pedal holding it to a metal bracket on the floor. You might need a pair of needle nose pliers to squeeze the clip

If what I think it broken then the pedal should lift right off the bracket. Look at the metal linkage bar, you should see a piece of plastic on the end. Twist it off.

Look at the new pedal that you bought (If) On the back you'll see the plastic piece thats broken. Its a tear drop shape so the pedal only goes on one way. Simply push it on and twist it to secure.

Put bottom back on over the bracket, reattach clip and put the floor mats back in.

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1982 300GD Carmine Red (DB3535) Cabriolet Parting Out
1990 300SEL Smoke Silver (Parting out)
1991 350SDL Blackberry Metallic (481)

"The thing is Bob, its not that I'm lazy...its that I just don't care."