So the question I then have is, how hard would it be to virtualise my current Ubuntu server within Proxmox, both not having dealt with VMs before and having spent a lot of time on the server?

This is maybe less of a gift than you think and can also be learned with practice. It’s about having a growth mindset. If you practice framing things in terms of growing ability then everything becomes achievable and the challenge becomes enjoyable.

It was though