Another option is to dual boot Windows XP and Linux. That might be best for you since you're a bit unsure about it all. That's what I did, I used linux online, then went offline when I went onto XP for anything. There's an article here:
http://www.zdnet.com/article/dual-bo...s-really-easy/
The article is a bit dated, from 2007, but should still be good I think for the gist of things. If you decide on installing a version of linux, then you could search for a more current article with the particular version of linux you choose and Windows XP.
There's an article to install Microsoft Office on Linux on How to Geek:
https://www.howtogeek.com/171565/how...fice-on-linux/
That's from 2013, but still should be useful.
There's an article here from a few years back with suggestions for people who still have XP after Microsoft support ended:
https://www.theguardian.com/technolo...nger-supported
In my case, my computer with XP on it was having issues(which is understating it, trust me) so I just went with a small light linux distro. Your computer sounds as if it is in better shape, so you might want to consider one of these:
https://fossbytes.com/best-linux-distro-beginners/
I have heard a few good things about ubuntu, though it's been a while since I've been reading up on anything linux related.
I can't find anything on Windows XP commercial or business user support being extended until 2020. I'm not trying to imply somebody gave you faulty info, because it's very possible that is correct and I just haven't been able to find it anywhere. I did see support for Windows 7 is until either 2019 or 2020, though. At any rate, I thought I'd give it a mention.
Have a good weekend.