They will usually quote you a price that takes into account bush removal taking a long time and may or may not charge you all of it if it happens to go well.
Providing them with replacement lollipops (inc. bushes) will save some labour cost, but best change the whole arm anyway as the ball joints will also have worn and aren't replaceable on the factory part. Meyle do a replacement wishbone with replaceable ball joints for a reasonable price (search for Meyle HD on ebay etc).
Both wishbones with all bushes and balljoints were replaced by an Indie on my last car in an hour. Removal of a problematic wishbone bush could take an hour on its own, depending on how competent the garage is.
