It took me about 3 hours. It would probably take the average person about 1.5-2 hours. I just work slowly and am very thorough.
It'* a huge benefit to have an extra set of hands. Muscling the tank around by yourself can be a real bear. If you have access to one, I strongly suggest a transmission jack. The flat plate on the jack is a real back and muscle saver....with or without the help of a buddy.
The biggest issues I ran into were the plastic "quick" connectors. I say that in quotes because they're not too quick to come apart after being on the car for six years. Mine were pretty corroded. Two broke in the disconnect process. I bought new Dorman ones from Napa. What I did was cut the sending unit galvanized fuel lines and lower the tank (after unplugging electrically, of course). That really opens up the area to work with those quick disconnect clips. And, it didn't matter to me since I put in a new sender too. If you're not putting in a new sender be prepared for some skinned knuckles as you try to work those clips loose.
The only other thing I did that was more of PM than anything else was to lightly use a steel brush and sand away some of the rust that developed above and around where the tank sits. I then sprayed it with flat black Rust Oleum to prevent any more rust. (My car had very, very little rust...I'm just anal).
Reinstallation was a snap. Of course, PB penetrant was my friend!