"I have found being very well prepared/educated and firm about pricing and what you want/what they can do is key,"
Sadly we need to be this at most places. This is why a relationship with a trusted service provider is priceless.
Last time I went to Discount to re-balance the KO2's on the 80 I showed them that their website only showed 15" tires for 80's and that they had the wrong torque spec (I brought the page from the FSM and the store manager called his boss about it)
My go-to has been Discount tire at 4850 Wadworth. I have used the hazard services while in other cities. Not critical, but nice to have.
I have used local tire shops on Sheridan in Edgewater and on south Broadway for $20 work I knew better than to bother any chain store, like mounting or dismounting Rising Sun or Craigslist purchased tires or swapping a rim on a 20 year old spare.
Last year I stumbled on an independent shop - Highway Autoworks at 4825 E Evans Ave, Denver, CO 80222. If you want 27" wheels for your hot rod / show car they have you covered. I was not sure what they would say to mounting a KM2 on a spare rim, but they handled it with ease. I went back there in early November to swap the Kenda Klever A/T2s onto my 80. I could have done it cheaper on Sheridan or South Broadway but I figured if they could handle those expensive exotic rims that they would do mine right. They did. Perfectly balanced. Nas is the owner's name, short for Nasser. I'm planning to go back there soon to mount the used Geolander G015's to the GX.
As a bonus Nas told me of a Syrian sweets shop 2160 S Holly St, Denver, CO 80222. Try the Kanafe and Baklava.