r134 recharge

How difficult is it to recharge my air cond.? It's a '99 w/R134. Also, I've had the the truck about 2yrs. and don't know if it has ever been recharged, is it normal to have to recharge it every few years? Thanks in advance!

If you don't know exactly what you're doing and/or don't have a set of gauges, let a shop do it. 134 isn't as forgiving as the old R12. If you overcharge just a little, you'll have very poor cooling performance from your system.
Every two years seems kind of often... I wouldn't be concerned about a '99 that's never been re-charged.

Thanks, I appreciate the advice.