In my city (Bath, UK) we've got an Apple retail store (been here a few months) and a Premium Reseller / Authorised service centre who have been here for ever.
So if the HDD / ODD is hard to get to (boo!), I'll just take it to the authorised service centre.... as they'll probably be cheaper than the Apple store!
Depends... Atleast here in PR resellers are more costly than the apple stores upstate since there in for profits. So it depends just ask them for a quote.