A cruciate rupture is almost never a same week emergency: waiting two to four weeks while you gather quotes, records and a second opinion does not meaningfully change the outcome. What you are trading over longer waits is arthritis, which builds steadily in an unstable knee, and muscle loss on the injured leg that makes recovery slower.
There are two genuine exceptions. A knee that suddenly gets dramatically worse may have torn the meniscus, which is painful and worth prompt review. And a dog that ruptures the second cruciate while you are waiting on the first becomes urgent because it now has no good back leg. Keep a waiting dog lean, rested and on pain relief, and treat any sudden change as a reason to call rather than wait.
Use the waiting time properly: get the records and x-rays, get a second quote from a different tier of provider, and have the diagnosis and technique choice reviewed independently. A month spent that way routinely saves thousands and sometimes changes the plan entirely.
Send what your vet said and quoted. A veterinary surgeon reads it and comes back to you with what they can do and what it would cost, before you pay anything. A written second opinion is from $250.
Send the case, hear back from a surgeon with what they can do and what it costs, and only pay if you go ahead.