1) There are several Canadian consulates in US for visitor visa. If you choose to walk in, you can get it back around noon. If you send it in mail, probably you'll get it back in a week. Here is the link to Canadain Consulate in Dallas, however, you can link it to any consulates in US, h t t p://w w w. d f a it -m a e c i. g c . c a / c a n - a m / d a l l a s/
2) About Automatic Visa Revalidation, if your old visa stamp in your passport reflects a different status with your current H1B normally you cannot use AVR. However,lots of people still can come back based on AVR using valid I94 due to the flixibility of border custom. You can refer to my old posting regarding this topic. Make sure you bring all your current documents to croos the border if you want use AVR.