I do not think it is necessary to pay any law firm for this process. 

There is a checklist and required documents in Canada immigration official page. You have to follow it whether you take lawyers or do it by yourself. 

After that its just a wait game. 

Law firm can't do anything after that either. You just have to wait for your turn. 

At first I was also thinking about law firm, but then I came across canada immigration forum. People over there help you with everything you need. Instead there are already 100s of thread that will explain the process. 

Do not waste $2,500 --- $3,000 with this law firm. 

This is just my thought.  

Goodluck everyone.