I would like to write some issue I know about upgrading the Exchange server 2010 to SP3.
First of all, I want to say that it is really easy to install the package. However, there are small problems you can see.
One of them is your account must be schema and Enterprise admin rights. Second thing is that if you have Endpoint protection, you have to uncheck Real-time protection. During the language section, it can get stuck and I know that some of my friends waited there 5-6 hours. If you disable real-time protection, it will 5-10 minutes.
Last thing I would like to mention here is that before starting the installation, stop all services of backup, antivirus software and anything that is related to Exchange server. Don’t worry, if you didn’t, the installation will warn you before starting.
the download path is http://www.microsoft.com/en-us/download/details.aspx?id=36768