The pumps are well known for burning out and going, so will probably need replacing. They normally burn out when over worked, this ties in with the leaky offside front strut as the pump could have continuously been trying to keep the strut filled with air. I would also get the garage to check the relay for the pump as the older ones are know to be faulty, the newer ones are the Hella relays, make sure to replace if not. These faulty relays also burn out the pump when gone.
If I recall correctly depending on where the damage is on the strut and were it is leaking from there is a remedy. The front struts are kown to leak at the top, open your bonnet and have a look at where the struts sit in the engine bay. A repair kit is avalibale from Merc dealers to repair the leaky strut if it is leaking from here as it is quite common for the seal to go here.
And finally i dont recommend replacing with a second hand part, the pump or the strut. It will probably cause more problems down the line. Parts will unfourtunately be quite expensive especially the strut. This is only if the strut is gone, it may just be the seal as mentioned, repair kits are around £80 plus VAT. Be sure not to get fobbed off and told its the whole strut when the seal may be the only thing thats gone, so be sure to check.
Im sure ive covered everything. Somone else may have some more info on here.
Good luck
