Thanks for asking and apologies for chiming in.
Just now I came across this ticket and let me share few resources with you that should help to upgrade website. First, I suggest you to setup a dev server and copy your website over that (please note that this is a optional step). But doing this has an advantage as in case any issue comesup, for theme and bundled plugins related problems you can get in touch with us and together we can troubleshoot the same without affecting the live website.
Next, to perform the update process we have compiled all the necessary and relevant information into a tutorial that I would like you to take a look before moving ahead.
Let us know how it goes and don't hesitate to get in touch with us in case you face any roadblock.