Hi,
I can do the upgrade for you. I will try it for free since I never used the CMS you use. but I know programming and other CMS quite well. I can assure that whatever I do, from the time I touch your site, I can restore it back as it was, coz I always do take backup of all. for this purpose, I would need SSH access to your hosting. It is always better to take backup daily or weekly, if you have a cloud hosting I can setup that for you. Automatic backup every week or daily
About the upgrade. there shouldnt be any issue unless you have some plugins that doesnt support 4.x of the version you want to upgrade to.
Thank you
Ahmed Hassan.