Yeah that's the thing with black nails. One of mine had black ones and I cut the quick by accident a few times. My first two dogs didn't have any but my second two did front and back! The boy I have now just has front dew claws. My vet is soooo expensive it's like £50 just for the consultation let alone anything else but I've been going since I was a teenager so stick with them as I do trust them.
£50 is soo expensive though! You're in the same area as me, I used to use the same vets for many years, what did it for me was my I had to put my boy pts, he loved riding in our truck, so I spoke to vet to have him pts in truck, she quibbled about it, but agreed, I'm in the back of truck holding him, she says better off in surgery, I'm like no ( he was really docile, lovely little dog) so she injects him, I'm holding him, reassuring him, crying, she's checking his mouth, then says, oh his teeth are quite worn down, probably cos of stones, I didn't pick up on that for a while, upset over losing my boy, but what the actual
duck, what a thing to say, and she'd been his vet for years, I ended up being so angry with them, I did complain to them, but they weren't interested, so moved my other dog to another practice, not keen on this one either.