Switching units within the Army Reserve. Is it eaiser than going active duty?

It all depends on your units organization/leadership, openings of positions for your MOS, and how much you are needed at your unit. I've been trying to transfer for a while, but with my rank right now, there are no open positions at the surrounding units for me to be accepted to. Just talk to your Retention NCO at your unit. They can do a search for open positions for specific MOS's in a specified region/state. 
As far as the process for it, and the time... can't help ya there since I haven't gotten that far myself.

Hope this info is helpful.

The process is rather easy. You need to see a retention individual and then they will start that side of the ball and then you need to get a form signed by your current command "releasing" you from your current unit and into your new unit.

It is based on vacancy and your command willing to let you leave. Best thing is start talking to your S1 and get all the facts, be nice to your NCO, 1SGT and CO.