In many ways, the upgrade to Dynamics CRM 2013 is less painful than the transition from version 3.0 to 4.0 or from 4.0 to Dynamics CRM 2011.In general, if your site has been already upgraded to CRM 2011 Rollup Update 12 or later, you shouldn’t experience significant issues with updating to CRM 2013.
The upgrade process falls into following large categories:
1.Find incompatible/legacy code and update it
2.Upgrade to 2013 (if using on-premise)
3.Review and refactor the user interface (UI) to adopt the new form and navigation paradigm.
Dynamics CRM 2013 removes all support from legacy 4.0 features. All references to objects like crmForm or 2007 web service endpoints such as ‘…/mscrmservices/2007/crmservice.asmx’; ISV folder, CRM 4.0 plugins are all unsupported and should be replaced with updated objects.
Use the Legacy Feature Check tool (http://go.microsoft.com/…