> I have a H4 visa but need to get a TN-1 to start a job.
> Does anyone know of any similar experience?
You should have no problems at all because nothing prevents you from getting a new visa.
> I live in Toronto. Can anyone suggest a better port of entry for me?
If your background is strong in terms of meeting TN requirement for your profession, it doesn't matter where you get it--they simply cannot deny you. But people reported less pleasent experience around Toronto area and I personally prefer Derby Line close to Montreal.
> Is it worth hiring a lawyer for a TN-1 visa application?
Again, if you meet the requirements, it is a waste of money.