Clarification of AOE2 HD ON STEAM

I hate steam. But I really want to play AOE2 again and I have a windows 10 surface pro 3 that won't run a legit CD version. I can't get it to work, I'm feeling like giving up and just buying the steam version. I only want to play offline. I don't care about tournaments or lans or anything. The single player AI and campaigns is all that interest me.

​

• Do I need to be signed on to steam to play offline?
• Does steam install software that runs in the background?
• Can I download the game from steam, install it, and then remove steam and it still work?
• Ultimately, If I buy this game through steam how much interaction do I need to have w/ steam?

thanks