GPS shopping what do you recommend for JMT yes or no on a GPS?

I am training and planning for JMT. I have read many different forums on gear and recently I read that it is essential to have a GPS. My sense of direction is bad as it is so I'm looking at a model that is not going to break my budget however I want it to be reliable. I am looking at the Garmin eTrex 10 Handheld GPS however i have to purchase and download the map from Garmin. I see that they have a PCT map but not JMT. Any suggestions as to if I should: 1) invest in a GPS 2) What model did you use 3) if you used the Garmin eTrex 10 GPS where you able to purchase and download the JMT map? Thank you.. My email is anotherpearlbdbxt@gmail.com