You will get no argument from me regarding the AR-5. It is a wonderful telescope! Highly underrated in my opinion as everyone seems to scramble after that extra inch and get the AR-6 - only to kick and scream that the mount is no good and it arrived out of collimation with it's collimation adjustable in the objective cell! See any linkage? I do! Hahaha!!! Anywho, the AR-5 is great.
I would suggest you get one new simply to have it under warranty on the off-chance anything goes wrong. May cost a little extra, but so would having that "Sword of Damacles" hanging over your head. And the eyepiece special is a powerful incentive as well. One thing you really should do, though, is to get a good 2" diagonal. The one that comes with it is pure trash. In fact I'll bet it is the mail reason people buy and then sell their AR-5 and 6 scopes. Hence the plethora on AstroMart. One look through that cheesy piece of plastic and out she goes!! Allow me to provide a link to William Optics and their 2" diagonal:
At $99, these are about as good as a TeleVue at a fraction of the cost. I have two of them. I would also suggest a good Barlow as using those short F.L. eyepieces can be a pain. Literally. For that I would suggest springing for a TeleVue for about $100. And while the mount can and does work well with the AR-5, anti-vibration pads will really help out. The cheapest source for these, and many other things you will find yourself wanting is Adorama in NYC:
As for set-up time? Take mount outside. Level same with a level facing North. at Polaris. Bring out scope. Put scope on mount and tighten 2 bolts. Align Polaris in the 8 x 50mm finder - excellent finder - and go cruising! Time? Under 5 minutes. I am sure you will have more questions and find things you will wish to improve. For instance I got an electric focuser from JMI so I don't have to touch the scope, and cause it to dance as I focus, as well as a handmade red oak tripod to add some height. To each his own. Just a fair warning: A telescope, any telescope, is just the beginning of a long and marvelous hobby!