Yes it is a waste, it will die with the first hard frost. Did you apply a pre-emergent?

I'm in the same boat, I think my back yard is 90% crab grass. I'm totally new to having a lawn (just bought the house last year) and I didn't think to apply something to it to prevent crab grass....next year (or do I apply this now?).

No I didn't apply a pre-m :( Live and learn!

If it dies, will it just eventually break down or am I gonna have clumps everywhere?

It actually depends. If you have a very thick stand of crabgrass and intend to overseed, it can be problematic.

The CG will make life tough for your new little seedlings to get established. If you can remove the CG by hand before overseeding, you will be helping yourself. You can also spray with RoundUp, give it a week to wither away, and then scalp the lawn with your mower before overseeding.

Once the first hard frost comes along, the CG is a goner but it will come back next year without treatment. Pulling the CG will only have a limited effect on the CG you see next year.

Apply pre emergent in Oct..About the end of Fed when the Bermuda is 100% dorment apply round up..Then in March apply pre emergent..Then in June I would aerate and apply some seed..

My advice is the opposite of everyone else's. Pull it up now so it doesn't reseed, and since the soil will already be disturbed from the weed pulling, plant grass seed in the bare spots where the crabgrass was. That's what I've done in the past, and it worked well. Fall planted grass seed has a better survival rate anyway.

Then in the spring put down pre-emergent.