You can mail first class from home! I figured it out and it saves me so much time since so many of my dipes have been going to CA.
You need to download the shipping assistant from USPS (vs. paying thru PP). You select "international label" and type in all the info and hit "calculate." Then, you print it off and it's a combined shipping label & customs form. You can't pay for the postage online, but you can use stamps. So, you just put the appropriate number of stamps on it (it takes 7 stamps to ship a GM to CA) and pop it in your mailbox. Easy peasy.
Re: PSA: You can ship first class to Canada from home!