Welcome. You got a good deal. I bought a brand new 2016 Rebel from a dealer, and got it OTD for $3495. I'm not a beginner, been riding for 44 years. I just love Rebels (the old school air cooled ones) and have had four.
I definitely recommend taking the MSF course, it will be the best money you ever spent. When I started riding on the street in the mid '70s, there was no MSF course (I took it many years later) but it was also a LOT less dangerous than it is today. Dumb drivers (which is most of them), distracted drivers (which is most of them) and drivers in a hurry to get nowhere fast (which is all of them) and a drastic increase in the amount of traffic on the roads has combined to make riding several times more dangerous than it used to be. After taking the MSF course and getting a good helmet, riding with the right attitude will likely do you more good than anything else. I personally don't believe the commonly held notion that all riders will eventually crash. After 44 years and close to a million miles of riding I have yet to crash on the street. And I am by no means alone. A lot of crashes are the same riders crashing over and over again. I have heard a lot of riders (yes, mostly sport bike riders) actually bragging about how many crashes they have survived. Must not be very good riders. But I do admit the odds are against you in todays world.
As for the bike, if it runs well, just keep it maintained by the book, except for changing the oil every 1000 miles. If you are going to let it sit for a prolonged time, definitely drain the tank and carb. Todays ethanol gas can do serious damage if left in there too long.
With a solo rider, the Rebel can handle highway riding. I weigh 240 pounds and have put around 30,000 highway miles on Rebel 250s. They will run forever at full throttle (well, almost) The biggest issue I've had with riding long distance on a Rebel is the extremely cramped riding position. I'm big, and don't fit very well. I got forward controls, and they help a lot. Some padding on the seat also helps. But you will definitely give out before the bike.
2016 Rebel, 2013 Royal Enfield B5, 2009 Genuine Stella, 2006 H-D Sportster 1200, 2006 Vespa GT200, 2001 Yamaha XT225
"I refuse to believe in a risk free society where the thrill of living is traded for the safety of existence." — Nick Ienatsch