I would say if you are going to do it, do it right the first time. As far as long range goes. To some people 150 to 200 yards is far. 600 yards is pretty far in most peoples book. I do shoot target out to 1000 yards and further. The furthest I have ever shot a animal is 635 yards. A buck deer is pretty small that far out.
You don't need anything special to mount a scope on a rifle straight. If you have a small level . Find a flat spot on the rifle and level it first. Now when you mount the scope do the same thing keeping the rifle straight. The kits come with small magnetic levels to make it easy.
If you need to barrow one just let us know. I am sure any of us would lend you one. What area are you from ? Most shops will also help you if you just ask them, Good luck.