If you are green and think a Tormach might be more than you can chew then you will choke on a DIY conversion. Learning CAD/CAM and machining will be enough of a mouthful.
The concept of "if I build it myself I'll be able to fix it myself" is flawed. Apply that philosophy to automobiles and where would you be. Learn how to fix it when it needs fixing, it's not rocket science.
Building it yourself is fine if you need another hobby. Your first conversion wouldn't be cheaper than a "ready to run", and if you cost in the man-hours it's out of the park.
I guess you know my recommendation.
Just some thoughts and opinions.
Phil