I'd suggest that being involved in football more generally is a good way to ease back in. Have you still been watching football on TV and/or playing at all? If so, I'd be surprised if you struggle (mentally at least) with the pace significantly more than you were when you took a break.
If no to the above, I'd suggest that you consider volunteering to do a match or two on the line as a club assistant for a local grassroots team. Most teams at that level have to rope subs into running the line for them and those subs will be grateful to have a few matches off. Tell the club you're a referee looking to get back up to speed - but don't make a big deal about being a qualified ref to the referee on the day and don't expect him to believe you!
When you do get back in the middle, you can really help yourself by being firm on dissent and abuse. Utilise the stepped approach - but if a quiet word doesn't calm things down, don't be afraid to ramp through 2 or 3 steps in response to the same incident until the message sinks in. Whenever I've had a tough match, I can almost always point to a moment where I tried to be diplomatic and would have made my life a lot easier by clamping down a little harder on an early moment of dissent.