I work high for a living. I climb all kinds of things. I do alot of roofs, but I'm used to them, and often wear no gear. Liability issues are making this change in every industry. I'm often bridging over open spans with a 40-75 foot drop and even in a harness, the sweat breaks out on my forehead for the first 3-5 minutes every time. I regard this reaction as healthy. I've never been hurt because I'm scared every time, and I channel this fear into caution while proceeding with work. I would advise you to proceed with caution, look into available safety equipment. Just to put it into perspective, my top of the line fall arrest harness and lanyard ONLY were about US$400. You'd also need a good climber's line and ascension tools.....another 200-300 minimum.
http://www.treeclimbing.com/content/blogcategory/39/82/
Depends a lot on how you are with height as well....
It is a lot easier to get somebody else to do it.