I have a plain vanilla site developed in version 4.2 and we are planning to migrate (upgrade that to version 9.2. Are there any major challenges to the process. If so, would you please give me a heads up or point me to some documentation that might be useful. Thanks a lot in advance for your valuable time.
Upgrade process from 4.2 to latest should be straight forward. Espesially if you have a plain vanilla website and don't have a lot of custom widgets.
Full documentation about upgrade process available here: http://docs.sitefinity.com/upgrade