US citizen, consultant in CAN - should I use S Corp?

[usconsultant]

I am a US citizen with an offer to work in Toronto, Canada for 1-2 years on NAFTA based work permit. I am trying to understand what the tax implications are and if the net income to me will be worthwhile to take the consulting offer. Here is my situation. I appreciate any help from this board.

SITUATION
- I will continue to have my home in US where my family will continue to live while I work in Canada for 1-2 years. I plan to be visiting US home once every 2-4 weeks; occasionally my family may visit me in Canada.

- I have an S corporation registered in North Carolina, USA. For any work I do through this company in the US, I pay corporate US taxes, and pay individual income taxes in the US on the amount I take as salary from the S corp (after deducting expenses)

QUESTIONS
- Is it beneficial for me to take the payment from the Canadian company through my S corp, or as an individual?

- What taxes (income, GST/PST etc.) I have to pay if I take payment from the Canadian client through my S corp in the US?

- What taxes (income, GST/PST etc.) I have to pay if I take payment from the Canadian client as an individual?

- I assume that I am not liable to pay retirement or healthcare contributions in Canada since I pay social security and medicate in the US. Is this correct? What filings will I have to make in this regard?

- The Canadian client has indicated that they will not make any withdrawal for me; I will be responsible for getting required waivers, licenses etc. What do I need to do so that the Canadian client does not make any withdrawals?

- Canadian client mentioned my getting WSIB Clearance? How long does this take? What do I have to do?

- Can you recommend any CPA/Legal firm that can advise me on these matters without charging a fortune (I know this is a subjective term)?

Thanks in advance.