Yes, you will be compensated and yes, any agreement you come to will be in writing.
Many people appear to use the University Land Board's Rate and Damage Schedule to negotiate their payments. I have attached a copy of it here.
They will more than likely be contacting all of the landowners along a fairly broad potential Right Of Way area to see who is cooperative and who is not. That may have some effect upon where their pipeline actually ends up going.
Hope this helps -
Charles Emery Tooke III
Certified Professional Landman
Fort Worth, Texas