@PbOak - I think you should be able to get most of you answers with a little research. It really depends on what Pi model you purchase. All the power requirements for each model are readily available with a Google search. The power supplies typically recommended are planning for the maximum power draw and not necessarily reflective of the actual power draw. Each persons setup is different. It's the same for a screen it depends on which model you purchase and then researching the technical specs.

The rest will require more planning on your part. Your estimated and peak power usage per day for lights, phone, etc. Calculating the watts per panel, battery size, battery capacity, battery banks, converters, etc. Mostly sunny days, cloudy.

I think most of the answers you'll need to research with your friend to fit your setup but to cover most Pi models a 5 to 5.1V, even 5.25V, 3A should do the trick. The rest is up to you! ;)