Here are some replace light options:
http://e-partssales.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=P&Category_Code=986lights
I would guess that the $300 price was not that far out-of-line considering parts are about $200. So, they added about $100 for labor. Most labor rates at the dealership exceed $200 per hour. Not cheap, but not completely outrages either, IMHO.