Ask HN: My first exit, I don't know what to do

Hello, throwaway account.

I worked for a company for a while, was offered stock options, bought the stock, left.

The company has been acquired and I`ve had a HUGE bundle of documents from the lawyers. I want to get my payout!

I`m totally lost as to what i need to do, are there any gotchas? Is there a time limit? The deal price is announced but hasn`t completed yet.

I'm in the UK but the company is in the US.

I suppose I should get legal advice but I don`t even know what kind of lawyer I could find would understand US corporate M&A law?

Any advice / things to read appreciated.