2000 Jeep Cherokee

I am thinking about purchasing a 2000 Jeep cherokee from a friend. She is selling it to me for $1700. At first thought, I'm getting a good deal, right? Well, there are some things that concern me and I need some advice from others who have this vehicle. The SUV has 204,000 miles on it; mostly highway due to her job. The most recent thing that happened to it is that it blew a cylinder.?.? I'm not sure exactly what that means for me as far as future use is concerned. Does that mean that there is engine damage already or engine damage lurking in the near future? I am a single mother and need something reliable but also at an affordable price. Also, she said her mechanic told her that the rear end is leaking. I'm not sure what that means either and if I should be getting that repaired immediately or not. Any advise from anyone would be greatly appreciated!