How to use an iPad for songs

After attending the Evart Funfest and watching people play in various jams, I've discovered that most people play by ear and seem to have an amazing inventory of songs in their head.   I'm not one of them.   Playing by ear will always be an extremely difficult challenge for me.   But I also observed musicians using their iPad with ease and seemingly being able to locate almost every song that was played by pulling it up on their iPad.  So, my question is where to start?   I do not own an iPad yet.   What kind should I get?   And which programs/apps are best for loading mountain dulcimer tab/chord sheets?  What do I need to know to get started using an iPad for music?   I would appreciate any advice on this topic.