H1B Traveling to Canada

I have an urgent question on H1B visa holder (no H1B stamp) traveling to Canada. My company will send to me to Canada for about one week. Do I need to apply for Canada visa? How long does it take to apply Canada visa? Where to mail the application? How long does that visa valid?

Also do I need to apply US visa to return? Somehow I have a feeling that I don’t have to apply US visa if returning within 30 days? Is it correct?

Any info is highly appreciated. If you have any good websites, please recommend to me also.

Thank you very much for your input.