Sorry if this has been covered elsewhere, but I like the look of the red-background Jaguar logo for the grill and the wheel center caps. How difficult is it to change out the black-background emblems for the red ones? Where is the best place to find these parts?

 

Both are dead easy to change.
Wheel centre caps - remove wheel and push cap out from the rear. A gentle tap with the butt end of a large screwdriver works for me.
Grille badge - held on with double-sided tape. Gently pry it off, preferably with a trim removal tool, but it can be done with a flat blade screwdriver wrapped in cloth. It has two locating tabs on the back so it (and the new one) can only go on the correct way.
Both the wheel centre caps and grille badge can be got from eBay or AliExpress, several listings for both. Two different size grille badges, 70 mm diameter for the "classic" (pre 2012) XF, 85 mm diameter for the "facelift" (2010 - 2015) XF, make sure you get the right one, if in doubt measure your existing badge.
You can easily paint the existing badge backing any colour you like, once off the badge comes apart into three pieces, the outer ring, the growler "face" and the backing. Just "flood" the backing with your chosen colour (and then coat with clear if you want), let it all dry and re-assemble the badge. The double-sided tape should have stayed stuck to the grille, so the badge just pushes back in to place.
Some of the cheaper Chinese wheel centre caps don't fit as tightly as they should, if so just stick a small piece of electrical tape on the outer edge of each "tang" before you push the cap onto the wheel.

 

Agree with the above. I managed to get off center caps using some sticky tabs without pulling off the wheels