Is the shock a stock one? if not just get the shock reconditioned, but depends on why it is leaking, if its overuse get both done, I had both done to be sure, look in yellow pages.
Child restraints are hard to fit cause you have to take out the parcel shelve and seats and get to them in the boot, they HAVE to be the right ones with the right bolts, washes but any compliance place should be able to fit them or know where to get them. try a search on here.