If you need info about being PR of Canada and driving US plated or Canadian Plated car to enter Canada you can calll
Fort Erie
60 Walnut Street
Fort Erie, ON L2A 5N7
Telephone:
(905) 994-6330 (Travellers)
(905) 994-6376 (Commercial)
Fax: (905) 994-6360
Niagara Falls
4551 Zimmerman Ave.
Niagara Falls, ON L2E 3M5
Telephone:
(905) 354-4843 (Travellers)
(905) 262-4642 (Commercial)
Fax: (905) 354-4956
I am not sure my one of friend told me that You can get Canadian Plated car at Naigara Falls Ny side and also at Buffalo airport.
regarding H1B stamping no need to inform Canada immigration it means your are not staying or working in Canada and you may face more questions.
Please note that if you try to get H1B visa stamp in Canada and you are refused you can not enter US, you have to go to your home countary then have to get H1B stamp, why cant you revalide in US from Deparment? you can get it revalidated in US if you have previus H1b visa in your passport or it has not been expired more than 1 year.