As soon as you go beyond a 100Mbps, it's advisable to change the reference bandwidth. If you don't, OSPF will not be able to distinguish between links greater than 100Mbps.
You don't need to get your provider to make changes to the reference bandwidth on their side. IN fact, they could be using non-Cisco devices that may not have any concept of reference bandwidth at all. As long as they have a consistent mechanism to assign OSPF costs to your links (which I'm sure they would), they do not need to change anything.
Hope that helps - pls rate the post if it does.
Paresh