Broken Mount , Dealer charge $900 ... Help

[H2Miami]

As I post early My H2 was having a bumping/knocking noise while driving around 50 mpg

I found the the differential rubber mount tear as shows in picture ..

Dealer ask my $110 for the new bushing and $720 for labor .. They said in order to replace the mount the whole differential needs to be removed ...

Please if someone knows if this is right or if any way to do it as a DIY job... I see $830 very pricey to replace a rubber bushing

BTW the guy in the dealer told me to rotate the tires to avoid the noise ,,, he said rubber may be worn but what is causing the noise is the vibration from a tire with a problem , makes sense to rotate the tires and see what happen ...