Hi bro.. Sorry I didn't check on your questions. If you buy the NAVPI from NAV's website the image will be pre installed. https://store.navcoin.org/product/navpi-stakebox/
Also you can buy your own PI and install the image. It's quite easy: https://github.com/NAVCoin/navpi/blob/master/README.md

Note: You can download the full node wallet as well. Rasp Pi is more secure but both run the same deamon.

for tutorials: https://navtechservers.com/video-tutorials/navpi/

Cost of electricity vs PI vs ROI: https://navtechservers.com/navtech-tools/staking-calculator/

Info how PoS work: https://steemit.com/cryptocurrency/@bocyaj/nav-coin-proof-of-stake-informational-guide

Join us in Telegram for more info:

https://t.me/navcoin