Well, this is an extremely complicated project. Maybe this helps you to get a bit further -> http://www.x.org/docs/AMD/R6xx_R7xx_3D.pdf
But I don't know how can you get the card to present the contents of the frame buffer on the screen.
And even if you managed to run the VS, PS kernels on the card, hand writing VLIW code is also not that easy.
What you're looking at here is really, really hard. However, don't let that discourage you. My advice would be to go look at the code for the Open Source Radeon driver, including the kernel mode components and the Mesa back end. Look here xorg/driver/xf86-video-ati - ATI video driver. The team is always looking for contributions. Writing an entire driver from scratch would be a massive undertaking. If you just want to learn about GPU architecture, contributing to the Open Source drivers would be a great way to do that. Go add a feature, tune performance or otherwise improve things. Feel free to ask questions.