Dufflespank, if $800 has you worried and you are saying you are going to convert to veggie oil, then me thinks you should not be driving a very very old MB.

No matter that they are robust, gas or diesel, you will be experiencing some repairs that will make $800 seem cheap by comparison. They are too numerous to list.

If it were me, I would find a locally well regarded independent shop to do this
job. Dealer will end up skinning you.

Maybe you should re-think the logic of cheap transportation and get a used Toyota with a uniform payment.

No offense meant, but these cars really do require a fair amount of maintenance dollars as the miles roll on.

Steve