2005 E320 CDI new fuel pump but fuel gauge not working right

[E300D]

Hi all,

Recently bought a 2005 E320 CDI with a noisy low pressure fuel pump in the tank..

I went to dealer and got a brand new in tank fuel pump along with a new seal.

My mechanic installed a new pump but now tells me the fuel gauge is not reading correct.

Is there a special way to adopt the new fuel pump into the system?

I am not sure how the new fuel pump/assembly on the right side of the tank affected the fuel sender unit on the left side of the tank..

Any help would be appreciated./