Call your vehicle insurance company and get a copy for Canada (it's yellow) just as a precaution.
On your mobile phone, see if they allow free texting. Sprint has a reduced Canada option for phone calls (it's like $3.99 +20 cents a minute), but free texting. Did a lot of texting on our last trip.
The food in Canada is reasonably priced, so I wouldn't try to take much across the border, but definetly not fruits/vegis. They can get picky on those. You can take quite a bit of fresh/frozen meat, but it's just as good in CA as the USA and bringing it back to the states can be difficult (not impossible).
It's worse coming back to the US, just plan on NO MEAT, VEGIS or FRUIT of the fresh or frozen variety when coming back to the states. Dried fruit seemed to be ok but the border guard had to think real hard about it.
As far as getting cash, find a bank in Canada or an ATM. The places near the border charge an extra fee that most banks don't. Banks/ATMS give the best rates from what we found lately.
2006 Gulfstream Ultra 6331
33' Super C
8.1L V8 Gas