When I first started planning my HT, all I owned was a screwdriver set and a hammer. I hadn't built anything since a lamp I made in junior high school. I spent 6-9 months doing nothing but reading this forum (probably an hour per day) and asking the occasionaly question. I don't think I ever even started a thread because most things had already been discussed - just had to search for them.
With the exception of the electrical work, I completed the whole thing myself in about 3 months (working on it the occasional weekend), so start to finish was under 1 year. In the process I accumulated several tools and couldn't be happier/prouder of the end result.
At first I thought there was no way I could do it after looking at my plan. When I envisioned having to build a riser, sheetrock over existing windows, build an equipment rack, build a half wall, build DVD storage units (built-ins), put up chair rail, put fabric on the walls, etc. I didn't think it was possible.
However, focusing on one thing at a time really helped. First thing I did was build the riser. I looked at many different risers here and did all the calculations for distance, height, materials, etc. Planned it out on paper, bought the wood and just started building it. Took me 1 whole weekend. After that I knew I could do everything else. You just have to study everything you're about to do and read as much as you can. Everything I drew, I went over a dozen times to see if there were errors. The saying is "measure twice, cut once", but for me it was "check everything 12 times, measure 8 times and cut once".