Tim,
There are two very easy ways (and maybe more by now) to do what you really want to do.
PDAnet with Foxfi
Easy Tether
PDAnet now includes Foxfi so, it does both a cable and a WiFi tether. If you use the wifi tether, you had better have power to the handset or it won't last long.
Easytether is cable tether only and it powers from the computer, I just have to remember to shut the screen down or the phone battery gets low.
Both are buy-once and then look out for your data limit (instead of 30$ a month and watch out for your data limit).
When we are traveling, I can burn 3g a month even if I can't find any 4G.
Matt