1. It is possible for your markings to be preserved since the provider will be using the MPLS EXP bits in order to provide appropriate service levels to your traffic. However, you need to verify that with your provider. There is a possibility that the provider re-marks the DSCP bits on egress. The important thing to understand here is what the provider expects to see from you in order to assign your traffic to the 3 different CoS it has. That is, you have to make sure that you purchase appropriate amounts of bandwidth for each required CoS from the provider. The provider will most likely police and mark your traffic at the PE. For example, the provider may have a gold CoS with which it associates all DSCP EF traffic. You have to then mark your traffic accordingly. Since your provider has 3 classes of service, you may have to aggregate your 10 classes into 3 that fit in with your provider model.
2. See above. Just because your DSCP markings are preserved does not mean that the provider will honour them within their core.
Hope that helps - pls rate the post if it does.
Paresh
