The initial build of it is relatively straight forward. Overall, I think if you have moderate mechanical ability, you can do it. I used Bob's post as a guide to get started (
http://forum.treasurenet.com/index.php?topic=393980.0).
The steps are:
1) Convert a quarter or nickel slot machine hopper into a dime hopper (if you are lucky, you might find a dime or penny hopper ready to go - I tried, but couldn't find one). Difficulty = 6 out of 10
2) Mount the hopper and a coin comparator to some sort of platform. Difficulty = 7 out of 10
3) Figure out how to get the coins from the hopper output to the comparator input reliably. Difficulty = 8 out of 10
4) Wire it to power. Difficulty = 7 out of 10
After the initial build of it, it takes some tweaking to address minor issues. After the initial build, I made minor mods to the feed slide and to the comparator. Before those mods, I would have some coins hang up at the entry to the comparator and get occasional clogs.
I would consider building them to order if the parts were more available. It seems that there are plenty of $0.25 hoppers, but the conversion parts are hit and miss. If anybody tries the build your own approach, I'll gladly offer advice and tips.