An 18 foot round pool should be very simple to install, I did my 30 foot round, the hardest part was the wall since it's one piece and weighed about 400 lbs, you wall might weigh 150-200 and that will be the toughest part since your site is allready level. - all I can say is spend the 800 on pool stuff or a the beginnings of a deck beside the pool - that way you won't regret it.
This will be a simple job if you're willing to sweat a bit for a day.