These things are all state by state, so checking that out is huge.
Your 401k will pass to whoever is the actual beneficiary. Your will won't matter for that. You could make your bank accounts POD (Pay On Death) which would make things simple. I have done that. I honestly haven't a clue how long insurance policies take to be paid out, since that's one thing I haven't dealt with.
I have dealt with the death of my younger son. Fortunately, he had a will, because when he turned 21 I sent him off to an attorney to write one as I had his older brother. I told him, somewhat jokingly, that he could leave his assets to a home for unwed cats, but it needed to be in writing. In the end, he left everything to his brother, which was appropriate. Even with a good will in place, and no complications, it took nearly a year for the probate to be completed.
Again, everything matters state by state. My son died in Oregon, and the law there provided that the executors of his will, me and my ex, his father, were able to charge the estate with our expenses (in my case flying from NM to OR and the cost of hotels and so on) and we were also compensated for our executor duties based on the value of his estate. That helped me out financially. I wound up not being out of pocket for my trip to OR for his life celebration, nor for the trip to KS for the same. And the extra for being an executor was honestly helpful.
When someone dies the costs of stuff: burial, cremation, memorial service; can really add up. It helps to be aware of that, which I think you already are. Honestly, if you want more from me, please PM me as I'd be happy to share things I'm not about to where everyone can read it.
I will say that making sure enough cash money is available for your funeral is a very good idea. Especially if those who would be dealing with the funeral simply don't have much money.
Another hugely important thing is to make sure that everyone who needs to know about your wishes and legal designations have that information. Several years ago, after my younger son died and I made a new will and trust documents, I sent copies of them to both my other son, and my sister who is essentially back-up inheritor. I also changed beneficiary on one policy to make her half beneficiary. For one thing, if I die while she's still around, she will almost inevitably help out in settling my estate. She deserve recompense for that.
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