It really depends on you, how far you are into the process, and how comfortable you are that your application won't run into problems.
You can make the change simply by contacting the CIC office handling your application and notifying them that you will no longer be using a representative. You'll also need to notify your representative so that they aren't confusing CIC by contacting them about your case.
Keep in mind that you may still owe some fees to your representative even if you don't continue to use them.
If I were you, I would at least wait until you receive initial approval of your application (i.e., when they ask for medicals, police records, etc.). By that time, it's much more unlikely that something will go wrong with your case.
