Before you think about lawyers, I would say be careful dealing with industry leaders because they may just be sniffing and not really serious. There are plenty of cases where a larger industry leader reaches out in disguise of acquisition and then gets the details and does it on their own. Not saying it is the case necessarily here but just be careful of that.
For example, ask yourself why they really need to buy you out. Why can't they build it themselves ? Is it really your customer base they want ? Is it your technology ? Do they just want you (acquihire) ? What is the moat here that they want to acquire you ? If you cannot answer that clearly, they may not be serious.
In terms of finding a lawyer, you need to find a lawyer who has experience in tech acquisitions especially in your jurisdiction/area (for example, in US, even the state of residence will come into play). Selling a business involves various things including whether it will be asset vs stock sale (you will need to learn the difference),what will be the terms (all cash upfront vs earn out/equity etc).
Be ready to spend $1000s or even $10,000+ on lawyers and the deal may still fall through. So are you ready to spend your own cash ($10,000+ or higher) and still be ready for the fact that deal falls ?
Just some things to keep in mind.