I usually cross-post Pinside listings with Facebook, and then only expand to Craigslist if I don't get any bites after a couple weeks. Pinside is good because you will avoid a lot of issues, since pinsiders generally know what they're buying and understand things break over time, and pinsiders know that moving a pin can sometimes shake loose a connector or a wire. I also like selling on Facebook Marketplace because it's very easy to communicate with potential buyers, and it's easy to spot scammers. Since you can look at the profile of your FB buyers, you can tell if they are a "real" person much more easily than through Craigslist.
The one big advantage that Craigslist has is that a lot of people looking to buy a pin will ONLY check Craigslist. (I never knew that FB Marketplace existed until I heard someone talk about it on Pinside about 6 months ago!) And I think you get more casual buyers on CL who might be willing to pay more for a given pin, or who will be more likely to overlook cosmetic issues that a collector pinhead wouldn't. But downsides are that you are more likely to run into potential scammers, and more likely to run into uneducated buyers that might have unrealistic expectations post-sale. So there's a little more risk, but I sold my last pin through CL and was very happy with the experience. So it's certainly a viable option.
Since it won't be easy for you to move the pins, just let the buyer do it. Garage-level loading is a perk for a buyer and could sway someone, but not enough for you to bother hurting yourself or spending money to move them up yourself. Just make it clear in your listing that you are unable to help load and that the buyer will need to bring enough help to move the game on their own. It will turn a few people off, but overall most interested buyers will still be interested in spite of the stairs.
Just my two cents! Good luck!