I recommend you read it all and take some time to digest it.
Don't do anything rash -- in fact, don't rush to do anything right away unless it's necessary. Necessary things include:
* Figuring out what your tax obligations are.
- You should get someone to recommend you a competent CPA who has dealt with this situation before. You want someone who will proactively help you sort out your tax situation starting NOW, not wait until tax time. But I would _not_ suggest a "wealth manager", or even a "financial advisor" at least to start with -- find someone who will just help you with the immediate tax consequences, and who will deal with you on a flat-fee basis with price given up front. A competent CPA should probably be able to handle this on a bare-bones basis for less than $1000, but _if_ you can get someone who comes highly-recommended and has significant experience with the specific issues you're facing, and can help you navigate the situation, paying a small multiple of that for more good advice won't kill you.
- Note that you are going to owe estimated taxes, which need to be paid quarter-by-quarter, not at tax time. At the federal level, you will not be subject to penalties, regardless of your income this year, as long as you prepay (in payroll withholding plus estimated tax payments) 110% of _last year's_ tax obligation. However, if you are in the state of California there is no such safe harbor for _state_ taxes if your income exceeds $1 million in a given year (which it will). (See https://www.bdcocpa.com/resources/articles/43 .) So make sure you pay California estimated taxes as promptly as you can manage. (But also, don't panic if you end up being charged penalties. For stuff like this (i.e. not fraud) they are generally quite small relative to the amount of taxes owed, especially if you aren't that late.)
* Figuring out your liquidity situation:
- Are you getting the money in cash, or liquid securities (i.e. that you will be able to sell easily), or illiquid securities (i.e. that you cannot reliably sell?) If your employer has been thoughtful towards you, you won't be in the third situation, which can be very messy come tax time. (If you are in that situation, there are people who can help advise you, but you'll want to start thinking _now_ about how you'll pay the taxes.)
- If you're getting securities (i.e. stock shares) that come to you in some sort of brokerage account, it's fine to _leave them there_ while you decide your next steps. Make sure you're able to sell enough to cover your tax bill, but you don't need to actually sell anything until you discuss it with your tax advisor.
- If you're getting cash, you will probably want to open a brokerage account to put it in (don't stick it in your checking account.) Charles Schwab and Fidelity are fine general-purpose brokers. Vanguard is good if your plan is to invest the money in low-fee index funds and then not touch it, which is generally a wise idea.