Archived and post-merger records are frequently the longest lead item in a file. Start retrieval before other preparation, and treat any translation or evaluation as work that can only begin once the underlying record is in hand.
Sequence retrieval first
Request the transcript and registrar letter as the first step, then use the waiting period to assemble employer documentation and confirm the profession's credential requirement. If the custodian cannot produce a record at all, that changes the strategy rather than the schedule, and it is better learned early than after a start date has been set with an employer.
Once the signed offer letter exists, apply at the port of entry shortly before the start date, or have the college file Form I-129 several months ahead. Once the record is stable, a Canadian outside the United States may request TN classification at a port of entry or the US employer may first file Form I-129; after approval of an advance petition, the Canadian must still seek admission. Once admitted, record the TN expiry and the licence and certification expiries side by side; the renewal sequence should begin several months before the earliest of them so the second entry does not repeat the first delay.