No financial affiliation or association but,

For strings I deal over the internet with Just Strings. Great prices, service and huge selection...and on par or cheaper (after factoring the exchange rate) than what I pay at a store near me.

For guitars, others have chimed in already about The Twelfth Fret in Toronto. I agree with all the comments regarding that place. Been dealing there for years.

For repairs, definitely Bruce Dowd, or The Twelfth Fret, or a great luthier who also does repair work on the side as well as fossilized ivory upgrades, etc. Alberico Guitars and Fabrizio Alberico.