1) Other than insurance and bike docs is there anything else needed?

Carnet? Not necessary, however.... having a carnet simplifies things if your bike is destroyed, stolen... I know that's not something you want to think about however there's value in a carnet, which is why when we travelled around South America we took out a carnet. Most frontier customs people know how to use it, a afew (very minor crossing points) need help. A few border crossings insist on a TIP, however this varies from crossing to crossing in the same country.

IDP - it's not often that a police check insists on it but it's cheap and easy to get and is your "plan B" in the event of being in the situation where your national licence is deemed unacceptable (we found it dealt with this situation in Paraguay once).

Medical cover - most needs can be handled by paying for the treatment however if (once again, it's to be hoped that this doesn't arise) you need major treatment and/or evacuation it's essential.

2) In your experiences is this doable?

Right now it's a big unknown, I know people who have given up trying to cross from Colombia to Ecuador and are shipping their vehicle home, for example. Land borders are now open into/out of Argentina, however others remain closed. As noted, things are improving, but be aware that there remain challenges.

Setting aside the pandemic, it's entirely doable - just a matter of resources. You presumably know that you'll have to ship around the Dárien... Mexico remains insecure in many places, however I know someone who rode from the USA to Panamá and back in the last month - it's a matter of common sense, situational awareness, and never, ever, riding at night.

3) Finally what time of year would you good people suggest?

I would plan on starting in Patagonia/Magellanes in summer - early, mid-, or late summer depending on how long you want to be there. I'd aim to be in Northern Argentina/Chile in Autumn. There's really no particular season to be anywhere else, although unsurfaced roads are affected by the rainy seasons in the sierras (Perú, Ecuador, Colombia).