I had almost the identical situation when I upgraded last year. They wanted 23,500, 63k kilometers, bone stock. I got them down to 21,500 and jumped on it. An unmolested Canadian GT is rare these days. I also bought it from a Ford dealership but the offered warranty meant I'd have to service the car with Ford technicians. These cars are a bit tricky so I would only want a GM warranty. I say go for it though and be prepared spend way more money on mods.
OGOC (Ontario G8 Owners Club)
09 PBM V6 (Traded)
GXP Diffuser, Mace Insulators, Solo, CAI, FE3, BMR, much more
09 WH GT, Solo Mach, HF Cats, CAI, LS3 Cam, Pat G Tuned, FE3, Whiteline, SuperPro, Centric/Hawk, DAI Autobahns 19x8.5/+35, RE760s