Hi
You have implied status as you have applied for a Study Permit not because you had one from before. You can attend classes unless you are told by CIC that your Study Permit has been denied. It usually takes around 45 days currently for a Study Permit to be issued. What you are asking them is for a change of Status from Work to Study. Since they issued you a Work Permit it is unlikely they will deny you a Study Permit.
The OP doesn;t have implied status for a study permit, s/he would have it if applying for an extension. The study permit expired in 2008 so is not apply for an extension.
PMM