I agree with
@grantctobin in that someone who describes himself as "overly cautious" might consider taking some time after learning the "introductory" stuff or basics of tech diving (notice I didn't say "fundamentals"

) before heading into AN/DP or other what I like to call "mechanics" of tech diving course. Take some time to practice those basic skills first. Once you have the tech mindset and the basics of buoyancy, trim, propulsion, gas management, etc., down pat, how to "do deco" should come easy.