For $100 your girlfriend
may have bought the cloud-based version of Microsoft Office Premium 365, which, as far as I can tell, can be used on up to five computers.
If that's the case, maybe you can get what you want from her.
You can check official prices/plans here:
https://www.microsoft.com/mac/buy
If you buy a software DVD here, you're buying pirated software. Most of the time it works, but not always (plus you need to be careful with Keygens in case of virus, trojans, malware, etc).
It is quite easy to find pirated versions of MS Office on the internet. However, some sites are potentially dangerous. Some of the better downloads from torrent sites may involve special installation procedures.
If you're new to this sort of stuff, it can be daunting. You could try Extratorrent (search in Google) - one of the better downloaders is ChingLiu.
Also, you need to ask yourself
which version of MS Office you really want/need. For example, I still use MSO 2007, which is perfectly fine for me. Newer versions often come out with a bunch of stuff that hardly anybody will ever need or use.
Unless there are significant changes in raw speed with the newer versions (as opposed to slowing your computer down even more), older versions are usually more snappier.
If you install a pirated copy, you may not be able to use any official MS up-dates.
Unfortunately, I can't help you with your issues on your macpro. I'm a Wintel person (PCs only). I "build" my computers myself and fix them when necessary.
I suggest that you find some Mac forum on the net and hopefully, you'll find ways to resolve your problems.
:cheerful: