Depends how bad the leak is. They usually condemn something as "leaking" if there's oil on it.
1) if your pwr steering resivoir is low enough to allow, add a bottle of stop-leak.
2) drive around for half an hour, leave overnight.
3) get under there and degrease it PROPERLY. clean EVERYTHING until it's spotless.
4) go for a drive with some nice corners. Do some 3-pointers.
5) park it, get under, have a look.
6) if the leak is bad enough that it's beading up to drip after a short drive,
a) see if it's coming from a hose (if it is, try tightening it or changing the hose)
b) if it's coming from the body of the rack, get it changed somewhere cheaper
7) if it ISN'T leaking visibly after your spirited drive and turning maneuvours, then just remember to degrease it again before your next rwc
edit: I remember a small fact that a RWC inspector once shared with me in Victoria. If you can thoroughly clean the underside of a car, drive it around the block, park it, get it up on the hoist, and not have any obvious leaks or beads of oil forming straight away, it can technically pass. This is how he passed my VP with a rear main leak. After a short drive, the outside of the main seal was moist with oil, but it wasn't wet to the point where it was forming a "run". That was a pass, and so no further work was needed.
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The 1972 HQ Kingswood
The 1989 VN Turbo Rally Project
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As for the price being fair, depends on whether he is fitting a reco or second hand rack....
Reco= fair price
Second hand= Ripping you a new one
I bought a reco rack of some guys on ebay that rebuild them, no change over and it was only like $250 it's a pretty simple job to bolt one in (loc tite everything)