So, normally this is a pretty easy DIY home project - and, once we got the troublesome lug off, the whole thing took us 30 minutes.
Unfortunately, it took about 5 hours to get the lug off.
Rust, corrosion, impossible access, faulty design (they don't use this type anymore!) meant that wrenches, sockets, hammers, basin wrenches, and everything else failed.
So, dremmel to the rescue! We had to cut through the metal. With zero access and no lighting. Oy.
What we grappled with:
The destroyed "lug of doom" (note the corrosion):
The lovely awesome amazing new faucet! (Again - but come on, this thing is a beaut!)