I just bought my first Land Rover this week (an LR4 like you) so I have some immediate tips, hope they help.
(1) I wouldn't buy an LR4 without having a Land Rover mechanic check it out. Our local independent LR mechanic saved me... I was very interested in an LR4 that looked great and drove well, with a good maintenance history and Carfax but fortunately I paid for an inspection and the mechanic saved me from buying a lemon (oil in the coolant, all cooling rubber tubes soft & squishy due to long-running oil exposure, possible major issues). Inspection cost ranges from $100-$200 but it can save you a lot. If you can't get an inspection, I just wouldn't buy it.
With the LR4 that I bought, I found an LR mechanic near the seller, and the seller took it in (they were several hours away from us). Clean bill of health!
(2) I also passed on one model because the Carfax showed it'd been in a front-end accident.
(3) On options, I landed a base model, 5 seater, with the cold-weather package. I'd rather spend money on lower mileage than options I don't need. The base model is a very nice car, beautiful leather and trim, and the basic sound system is great.
(FWIW, I grew up near where you live and I do think the cold-weather package would be worth it... saves on scraping ice.)
(4) There are a lot of 2015 LR4s (mostly HSEs) coming on the market right now, I think because their leases and 3-year/50k mile warranties are running out, so it's a good time to be looking. In my experience there were quite a few coming up at auction; you may be able to find a wholesaler or used car dealer that can look at those for you. Even though I didn't ultimately buy from them, one of our local dealers was helpful and proactive about finding me several options.
(5) Road salt, I think it's used in Thunder Bay. If you're buying a used LR4 whose original home was Miami or Texas, I'm not sure whether there are concerns bringing it into a salty environment. I had the opposite concern (LR4s whose original homes included road salt), so I can't give good advice on what you should look for, but you can probably call a dealership and ask what they'd recommend.
(6) I've had two mechanics now recommend after-market extended warranties. I'm still researching options, but the feedback was that they'd pay for themselves and de-risk the entire purchase. Both mechanics offered to review the exclusions/inclusions to make sure it was good coverage for an LR4.
Hope this was helpful, and hope you end up finding a solid option.