A local dealer had a lot of quality Canadian large denomination currency come back from grading, most all were mintstate and epq/ppq. Where would you go for valuations on these, Heritage? Track and Price?
Auctions, like anything else. Look at Heritage and Canadian Numismatic Co. to start.
Most local dealers have catalogues & he should be checking his Charlton (the best option) as a starting point.
Without that, he can check "coinsandcanada" https://coinsandcanada.com/banknotes-articles.php?article=how-much-my-canadian-banknote-is-worth?&id=484 but they tend to be very generous (to what is actually market value). PMG Population Report site also shows similar notes on the market once you've selected the note in question https://pmgnotes.com/population-report/canada/