Figure out what percentage of the company you own. Saying you have something like 50,000 options is meaningless unless you know what others own. 50,000 options could be .001% of the company or it could be 10%. You have no idea.
They'll probably hate you if you ask to see the CAP table, but that's the info you want. Don't be shocked if your options end up being less than 1% of the company even if you were one of the first 10 employees.
Personally, I was part of a 15 person angel-funded startup that sold to a private company for 30mm at the direction of a VC firm. They bought out all of my options at full value.
I had less than 1% equity. I didn't get much money but got about enough to make my salary what it would have been if I'd been working for a bigger company. That's it, but it was about what I expected and seemed fair given how my salary/options were presented to me when I was hired.
Once sold, the new company will either fire you pretty quickly (within 6 months), or will create some silly incentive plan to try to get you to stay. I stayed on with about a 20% salary increase, which brought my salary up to the market rate for a big company. I was happy with this agreement.
Be prepared for a lot of office politics and difficulty integrating with the acquiring company. This will be the hardest part. It's substantially more complicated than the financial part of the sale.