If you're new, you think you're likely to stick with the hobby for a while, and you have a bit of disposable income, I'd recommend going with a tank controller up front. Then all of the money you would spend on temp controller, light timers, etc, will be built into a decent controller. I'm not saying it will necessarily save you money, but it will make things easier up front and will help get around the temp issue.
On the glass thermometer... you might not want to trust that digital thermometer as much as you seem to be. Like fishdoc said, I'd take the consensus. I have a digital that consistently reads 2.5 degrees higher then all of my glass thermometers and about 2.0 higher than another brand digital I have. Here's my thought... they've been making glass thermometers for a lot longer than digital ones... so if you have 3 different brands of glass thermometers reading the same, I'd have to think they are pretty darn close. In any case, it can't hurt to have more than one thermometer, so leave the glass one in there and see how it reacts to temp differences in comparison to the digital.