We are glad you are considering moving to Telerik OpenAccess ORM.
I think a good starting point for you will be to have a look at our N-Tier examples. We have put a lot of work into implementing comprehensive and well designed examples including WPF and WCF Plain services, WPF and WCF DataServices, SL and WCF RIA Services examples all built on top of MVVM. You will be able to find them (and a lot more examples) in our SDK.
In the end it is pretty straight forward to map you database with OpenAccess and then use a custom T4 template that we provide in order to generate DTOs and expose them trough a service. As to validation currently we do not provide anything in regard to entity properties however we have planned development on the matter in the near future. And as to change tracking it can be easily achieved by accessing the inner scope object of the context that has the tracking interface exposed, if you need more info on the matter please say so. Or you can retrieve the changes that are planned for the next commit and use that information.
Please have a look at our examples and get back to us if you need further assistance, we are looking forward to hearing from you.
All the best,
the Telerik team