That's where I was going to go with it too....but given the way case measurements can vary....a solid baseline sounded pertinent.
It should be pretty cheap to do it! I would make sure that they are going to do it on a lathe as typically it stays a little more concentric. With that being said I have seen a couple of them be done by hand and it is pretty self-explanatory if you wanted to go that route. If you do that, you will have to take the barrel off and get the proper tools for throating. You will need two resized cases so they shoulder up without any pressure. Check and make sure they both shoulder up before you put a bullet in the one! Then put a bullet in one at your desired seating depth. You will then take the empty case and put it in the chamber. Measure from the back of the case to the end of the barrel. Then put your case with a bullet in it and stick it in until you feel a small amount of pressure. Measure to the same spot and subtract the difference. You can keep doing that until the two cases measure the same and that is when you know you are not touching lands anymore. Add how much jump you want and you are good to go! Measure twice and cut once! Also, take into account throat erosion if you are planning on shooting it a lot and want to stay close to the lands. I typically start a fresh barrel at .020 under my desired seating depth so if you are chasing lands you are not ever seating your bullets out too far.
My farrier makes shoeing my horses look super easy too!
I considered it, being handy with most tools myself, but I think I'd much rather leave something this precise to someone who's done it before. By the time I've bought a comparator, rented a reamer & gathered the necessary testicular fortitude....... yeah. Probably better off giving the money to someone with a bit of experience I reckon.
