SAS's architecture has become increasingly complex in the Version 9 era and hence applying maintenance and doing upgrades have become more complex also. So I'd be very wary of DIY upgrades unless you have had some prior experience of server software installs. This post and the link to the software upgrade guide will give you some idea of what you are in for:
In our experience it can be more cost effective to do a brand-new and separate VA software install than to upgrade an existing version. I understand SAS is working to make upgrades much easier and less expensive but until then we just have to deal with the current complexities.
the quick answer to your question is that, generally, yes, it is fairly easy, although there are some considerations to make, related to architectural customizations you might have, such as:
Do you hav Single Sign on or any kind of Web Authentication set up? Or is it authentication just towards the metadata?
If you have HTTPS/SSL certificates, have those been set manually, or during the deployment? Since 7.1 I guess it was a manual action.
Do you have a Reverse Proxy? If your users can access from internet besides internal connection, you might have one.
If you are under any of those scenarios, you will need to revert back those changes, then make the update.
And thing is, if you make a new installation, as @SASKiwi indicated, you will need to make the changes as well (with the difference that this time the SSL certificate you can add it during the deployment, a good new feature).
If you ask me, and as I see you do not feel fully comfortable with this task, I would strongly recommend you to get 1 day assesment from SAS Consulting services or consulting services from a specialized partner on installations. They will be able to assess the best approach and let you know if you can do this by yourself, if you need any assistance, and the best approach while providing the best quality.
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