Good afternoon guys'
Is it hard to rebuild the calipers (rear) on a 1988 560SEL?

Also the self adjusting leveling valve needs to be replaced...both of the above as per the mechanic who just said the same about the front and replaced the front calipers to the tune of 600 bucks. They say the rear boots on the calipers are cracking and the leveling valve is leaking and the estimate is $1100. Any input would be appreciated.
Thanks

Brian