Sorry to hear you have cancer of all things. What a terrible terrible ordeal to have to go through. Switching over to vaping will help to put some calm moments back into your life as you contentedly vape your favorite juice. The eGo is a great starter kit device, which is also still used by many veterans of vape. They have wonderful flavor, fast charging, and good life. I still love mine even after all these other mods I've collected since.
You can drip into a carto to top it off but first you remove the drip tip ( you hopefully replaced the little white seal ring plug with a mouthpiece/driptip). Remove the DT, tilt it sideways and drip fresh juice into it like you are pouring a beer, with the goal of keeping juice out of the little hole. If you do get juice down the middle, just blow it out. It might gurgle a bit for a few vapes, but it'll recover eventually).
Welcome to VT!!