I did this job not too long ago on a Q45.... it was sort of a hybrid of me and the shop...

I did all of the work... and then took it to them to "pull a vacuum" and to install the cooling product.

As a 300e owner.... I decided not to purchase a car unless it had the A/C re-done.

I know if you have a pre-existing situation that would be impossible. If I had a 300e and it needed A/C work..I would do it myself..because no job should be done without going after the evaoporator... and I am told that is a 12 hour job... leaving it to a professional would be cost prohibitive..

I have receipts totaling 2900 for compressor, drier, the a/c manifold hose, evaporator/expansion valve... so it is involved.

If you have a 190e, I understand you can get to the evaporator through the firewall...much better design.