have you already found the SAS Guide to Software Updates manual? If not, I would like to highly recommend you to Google it and give it a look. It should be able to answer all or most of your questions. If you come across any more specific question, please let us know 🙂
In regards to that error, it woould help us if you share the full error message, ok?
It is not clear if this upgrade is for windows/Linux/Mainframe server installation or on the single/multiple machines. Please clarify what is the imapct size. There are list of activities you need to perform before you start your upgrade. Probably we can discuss in detail, once you answer the first question.