So i am scouring the internet for an idea how to transform my old g4 i mac into an apple tv of sorts mainly a computer that is able to play video full screen on an hd tv would be nice hopping that i can accomplish this for less then a mac mini

Not really. The AppleTV software can run on an Intel 10.4.XX machine. You can use the Mac Mini with its native Frontrow application. It's not going to be anywhere near HD. The $200 or so for an AppleTV is worth it.

your options given you currently have a ppc are:

run Leopard, its Front Row will work on PPC and resembles appletv 1.0

or build a hackintosh. the dual-core atom boards are cheap and work well.

good luck

the leopard on ppc option is not viable, for one afaik most of the plugins for appletv that are leopard compatible have not been compiled universally, and on top of that not all of the plugins are even leopard compatible.