- How long will it take me to level to 60?
Depends on you , if you play on monster power 10 with friends that have some gear to advance fast through it , then it won't take much.
Also if you are being boosted , it takes few hours , if you wanna explore everything and play it on relax mode , it can take a while.
I wouldn't worry about that , just play and enjoy the game , don't rush to 60.
- What is the 'easiest' class to learn the game?
There is no easy class , play what you like.
Melee classes are harder at first because you don't have gear and you can't kite around while dealing damage , so that might be an answer.
But also I noticed that Barbarians and Monks are easy to gear up at 60 to be able to farm effeciently at higher Monster Power.
In europe you can gear up your monk with 500k-1M gold to farm mp5-6.
Ranged classes can get away with less survivability gear for more damage though , also CM Wizards can tank anything with very cheap gear( I consider them melee not ranged).