RE: Some simple help needed
If you're going to teach yourself to fly, you should be looking at something that can sustain many hard crashes and tree encounters. You'll probably be looking for a plane made out of foam - preferably EPP (translucent resilient) and not EPS (white brittle). I'm sure there are a few planes that fit this description but I can whole heartedly recommend the Unicorn flying wing (unicornwings.net). They are flying wings and hence don't look like normal planes but you should be able to find out if you like flying in a hurry. The Unicorn is super easily contructed, floats forever (in the air but water too probably), flies about 15 minutes on a charge, and can take a crash unlike any other. Again and again and again . . . I've moved on but I still use this plane to practice slow and low flying and maneuvers - and crashing. Your 100' x 400' area should not be a problem as long as you resist the urge to fly too far in a straight line. You'll need a 3-channel radio with elevon mixing to fly this plane plus a battery charger and a bunch of tape and glue - pretty slim initial investment compared to wet planes.
Danno