What forms to get paid - Help!

I am a CDN management consultant. I have TN1 visa. This is my 1st week of work and paperwork is still not locked down. I am employed by a placement agency providing my services to a client / customer. I am currently in USA for Orientation and realted. I will only be in the USA for 1-2 days a week for the duration of my contract. Otherwise I am in Canada doing to bulk of work in home office . My employer appears to have little experience with handling this situation so I am having to dig to get answers. What paperwork do I need completed and where does it get sent?
Do I just fill in a w-9 while I wait for some documentation to arrive related to SSN?
How do I get a SSN from states? What are my considerations?
Is an ITIN what I need?
It appears I cant get paid until this is sorted

You certainly do not need SSN to get paid.

You are entitled to SSN, and should be applying for one. In the meantime, your agency should pay you as "pending SSN", or, simpler, just give you cash advance until your SSN is in.

You don't use W-9 for employment.

How do you get SSN? Type "apply for SSN" in google and read for yourself!

I recently performed an original song on a U.S. program for NBC. The filming was in Toronto, On. We negotiated an amount for using my song in the program and now NBC is ready to make that payment.They have contacted me and are saying I need a EIN (Employment Identification Number) and I need to fill a W- 8BEN or they will have to withhold 30%. Do I need to do both of these or would just the W-BEN be enough

W8-BEN will be enough It allows for foreign ID (your SIN),