Based on a quick search, here's what I found.
I found a few options that might be helpful for locating a space with a lift where you can work on your cars in the Charlotte or Gastonia, NC areas. While I couldn't find a specific listing with the exact serial numbers you mentioned, there are DIY auto repair shops and garages that offer lift and bay rentals which could serve your needs:
Elevate Garage offers tools, lifts, and bay rentals for DIY auto repairs, including knowledgeable staff and classes. This could be a great option for working on your Chrysler 300C and Mercury Mountaineer. You can book online and find more information on their website: Elevate Garage.
You may also want to check out Garage Yourself and similar DIY garage spaces that charge by the hour for lift usage, which can include additional services like tool rentals and oil disposal. While the specific site visited was not mentioned, facilities like Garage Yourself typically charge around $30 an hour, making it a cost-effective option for short-term projects.
Given the specific repairs you mentioned, such as replacing an O2 sensor, shocks, and brake pads and rotors, a DIY garage space with a lift can significantly ease the process. It's advisable to contact these locations directly to confirm availability, rates, and any specific tools or assistance they can provide for your vehicle models.
Remember, when working on vehicles, especially for tasks like replacing catalytic converters or working with suspension components, having access to the right tools and a safe, equipped environment is crucial for both the quality of the work and your safety.