it is common but only because the pas fluid doesn't get changed when it should.

if its only just started doing it as you say then a full flush and fluid change should prolong the racks life a fair bit so get it changed ASAP mate!

if the rack does need replacing at some point, either because replacing the fluid didn't work or the problem has resurfaced some time after a fluid change, then its not that hard a job so don't panic yourself about it. i got a replacement from a breakers for £64 with 90 day warrenty and did it myself on the drive. it does require the subframe to be dropped but reaignment isn't an issue if you refit the bolts in the same holes and realign them to the marks on the subframe.

good luck with it and its certainly worth doing if the shell is mint.