2000 Grand Marquis wobble / swaying

Sounds like you need to have your hubby bring the car back and have some front end work done, possible you need struts !

Make sure lug nuts are tight.

enginecreator, please give a gal a little more cred than that! But thanks

so, struts and tie rods? Is that something I can do in my garage? Or do I have to take it to a professional?

Take it to an alignment shop to get it evaluated. Yes loose lug nuts can cause this and it has happened before. Also the tire pressure should be checked.

your new tires will have more "grip" than older worn tires, so any alignment issues will feel more pronounced then when you had the old tires on the car. Look at the old tires, if you see them unevenly worn then you definitely had a bad alignment. If you do replace something like tie rods, you'll need an alignment afterwards, so it can be cheaper and more convenient to have that type of work done there to begin with. You don't mention any noises, like squeaks or clunking, sometimes associated with bad sway links, bushings, or struts. But whatever the cause, just get the front end checked out and you'll be good to go.

PS if you just bought new tires, ask the place that sold them to you for a referral discount to any shops they might use. I usually get 20% off alignments from the place I buy tires from.