I can guess at what grill you have, but can you provide pictures of what grill you want? That would help a lot indetermining what you need to do to get it. Same for the bumper.
There were a few variations of Ranger grill that had a mesh style and they take different components to install on your 2006. I'm not entirely sure what you mean by "slimmer" bumper, but again there were a few different styles and they take different components. It's possible to install any combination (98+ parts) on your truck, just a matter of knowing what else is necessary to make it fit. Maybe hood or fenders, maybe header panel or headlights.
FWIW I'm wanting to restyle the front of my 99 too and it'll take replacing basically everything except the fenders to get the look I want.
Also trying to change the wheels to something a little bigger but not so big that it looks stupid, but I'll spare you all another "biggest tire for a stock ranger" thread. Thanks in advance.
Bigger wheels or bigger tires? Is the goal a taller ride height, less open space in the wheel wheels, or just bigger wheels?
You can definitely run taller tires (I can't give sizes), but as noted you need to take it into account in braking allowances. If you're just looking for less open space, have you considered mildly lowering the truck? IMO it's a better and better looking solution for that than taller tires.
You can run bigger wheels without changing anythng else, you just need to determine the proper tire size to match the diameter that is there. Or you can run bigger wheels with either a taller or shorter tire.
Picture is worth 1000 words. Have you got a photo example of a Ranger with the styling you are after?