How to safely revamp your PPC campaigns

I've been handling our paid search campaigns for a little over 2 years now. We don't have a huge budget, roughly about $3000 a month. I'm getting to the point where for the first time I'd like to totally revamp the structure of the campaigns to make better use of the budget, but I'm a little hesitant to "screw everything up".

Can anyone point me to any resources or provide any suggestions on the best way to go about this?