Matt - I have that exact same Graco you linked to.
Shop around and see what HD and Menards sell it for. IIRC, I paid $199 for mine.

They work perfect for the size job you're planning.

After you're done using it, flush it well with water, then change over to mineral spirits and flush it with that & store it with MS.

Antifreeze will also work - - but - -I hate using that because it's so nasty if a pet gets into it. There are some non-toxic antifreezes, but, they run more than MS.

Personally, I'd hang onto it & not sell it. An airless is one of those tools that you never know when you'll need it again, but, when it pops up, you'll be glad you have it.