As I told you before, if you DIY (do it yourself), you will have to read tons of materials in English. You have to understand every word. From my own experience, such reading is extremely VALUABLE! Remember, once you come to Canada, there won't be any translation for you and soon you'll meet trouble in almost everything if your English is not good enough.
The agent can do nothing for you to improve your English than DIY. The ONLY difference is you spend money and you lose an opportunity to practise your English ability. Of couse, if you have good money and don't care, that's another world. But I suppose you're just like us, average people. Every dollar is valuable here. Save it before you come.
Anybody with your background can easily get approve if he apply for immigration. It depends on your background only, not on the agent.
2, Inprove your English, try to describe your work in English freely.
3, Your fate is in your own hands.