I mean if you're coming from the view of "does this change now have an effect on the whole organism" the answer would be yeah kinda. If you wanted to delete a gene and see what effect it had, if you only cha get one cell's genome, you'll never see an effect because it's just one cell out of millions/billions/trillions. On the other hand, if you inject the CRISPR stuff in a fertilized egg at the si gle cell stage, that cell will divide a bunch and then all the cells will have the deletion. Those are the two extremes, so you can target stem cells or remove blood cells and return them, but the idea is the same: you need to change enough of the correct cells to see an effect

You're right, all of these processes require that you have all the bits in the right place at the right time and the cell does the right thing and no enzyme messes up too hard. So you shove as much stuff in as you can to maximize your chances When I would try to insert a mutation in a zebrafish, I would inject hundreds of fertilized eggs at the single cell stage, let them grow up, and then take a tail clipping to genotype. I'd be lucky if I got a couple successful mutations from those hundreds of eggs. It's definitely a numbers game.

Caveat: this was like 6 years ago, when it was relatively new. Success rates have likely gone up as the technique has been refined but general principle remains

Make sure you include property taxes and insurance in those calculations plus extra left over to save for when things break. What kind of down-payment will you make? How much in savings will you have earmarked for fixes (which should also be separate from your emergency fund)