Which should I replace 1st, the countertops or the backsplash?

Do the backsplash first, move cabinets away from wall just so the backsplash is covered on the bottom that !ets the cabinets cover over the backsplash. Contact paper is very hard to do. Your going to cover the counters, I hope you know how to do this. I did my cabinets with contact, and ,,, I'm pretty good, your brave to do counter tops. My suggestion is cut out the paper, and lay it with the backside up to see how well it will fit.

Countertops everytime

countertop then backsplash

Countertop first always. Different tops have different thicknesses, you don’t want to put the time into a backsplash then have to pull some off, add to it, or redo it all together because of your top being to thick or to thin, and you really don’t want to be limited as to what you can use for a countertop because you’re trying to match it to fit the gap between you cupboards and your backsplash!

I was in the granite countertop business and always recommended that the countertop be installed first. This way the wall tile or backsplash will lay on top of the countertop. This will prevent liquids from seeping behind the countertop.

I would replace countertops first...there may be a difference in the width of the back of the counter thereby creating a gap that is easier fixed later

Definitely the countertop first. In order to install the backsplash properly you need to have the countertop to measure against.

Countertops are always first as the thickness of the material you'll be adding to the top of the base cabinets will vary. You will want to start your backsplash at the height of the countertop and go up to the bottom of your base cabinets.