When we purchased our trailer in Delaware for export to Canada the dealer provided us with a temporary tag, somewhere in the $90 range I seem to remember. Could Inland RV help you in that respect?
And sales tax for us wasn't an issue as Delaware has no sales tax - but again, couldn't the dealer you're picking it up from give you some advice/information?
In case you need some info on importing into Canada, I detailed my experiences
here. It's a step by step outline, and I've indicated a few glitches that happened that could have been avoided.