Very sorry to hear about your wife. My sincere condolences.
You can use the CS slot in Panel Programming to make your Panel call your cell phone, but I don't recommend it: The Panel is programmed in firmware (can't be changed) so that if it doesn't get through to the CS (doesn't get a "handshake"), then it tries to call 8 times. That means that you would get 8 calls in succession from your Panel every time it tries to report an event; which would be a much bigger nuisance than powering the panel down and back to reset the comm fail. Getting 8 phone calls in succession gets old real fast.
Now that I've had a little time to think about it, the simplest way to have your panel initiate a phone call to your cell would be a stand-alone dialer, triggered by the bell/siren output (T3 & T4 on the terminal strip of the Vista-20).
Full disclosure, I've haven't used a stand-alone dialer, since I worked for professional dealers that exclusively used Central Monitoring Stations; so I can't vouch for their efficacy. However, I've read on the DIY forums I post on that they're a viable self-monitoring method, and there are reputable brand names that make them for exactly this application. A quick search turned up new and used dialers for between ~$40 (used) to $140 (new). If this interests you, here is an example I found on eBay:
https://www.ebay.com/itm/UNITED-SECURITY-AVD-45B-AUTOMATIC-VOICE-DIALER/124083803562
It's used and doesn't seem to come with a manual, but I located that here:
https://www.onsetcomp.com/files/manual_pdfs/AVD_45b_manual.pdf
It also doesn't come with a phone cord, but someone with your background probably won't have trouble locating the proper one.
That's just one example I found, you can search around for others.
Again: I can't personally vouch for its efficacy, but United Service Products is a brand name in the alarm industry and I can vouch for the general quality of their products.
About replacing your Vista-20 for a newer Vista-20P, instead of using a stand-alone dialer: I may have overstated the simplicity of replacing your Panel. The hardware itself would be easy enough to replace, but the new Vista-20P Panel would need to be programmed from scratch: There would be a learning curve on the Panel Programming, because professional-grade alarm panels are not meant for DIYers and the manuals assume a certain familiarity with alarm protocol and jargon, etc--they're written for experienced techs. The manual isn't incomprehensible, but there IS a learning curve to get past, especially when it comes to setting values for the Zones in your system (Zone Types, etc). Which is why I suggested the stand-alone dialer: That would be just a matter of wiring it onto the panel and programming numbers into the dialer, and (I suppose) recording a voice message (or not): No Panel programming involved.
Let me know what looks best to you, and I'll be happy to advise you about getting what you need.
EDIT: I sent you a PM. Check your Inbox.