That is really not going to be too easy.
The problem is that VGA signals are pixel and row oriented, rather than character or vector based. You can do it (http://www.embedds.com/simple-pic-vga-tester/
] is an example) but frankly I think you will be using most of your processing capacity just servicing the video signal and converting your display to video signal format.
There are simpler ways: you can get LCD modules that are character or graphics based and include an LCD controller to take the load off your processor. Might be a lot cheaper and quicker to interface!