The 'clunk' you hear is the bad N2 cells...as said the the 'hydro-struts' are pretty long lived and if there is no leaks then they are prolly good. They are expensive new tho if you do need, but I'm betting they are fine. While its aparts and depressurized you may want to change out the $5 rubber bushings above and below the 'shocks' back there also.
$2100 would be an ultimate soak and the whoever charges you that would prolly take the rest of the week off for what should be only a few hours of work. Run !
You or your indy can do those cells in your driveway not even jacking the car up...its pretty easy with no special tools. Do a search here, I'll bet there is a good DIY description. Properly bleeding the system when you are done is critical also...but easy as well.
I've done it on 3 500Es and I'm no mechanic by any stretch.
