Is it a no brainer to attend law school? Short answer, NO, NO, NO! Don't go into law school assuming that it's a "no brainer".
I can honestly say, my law school certainly required a lot of my brain cells. (Well, if you are smart enough, you might feel like you can pass or ace law classes without using much brain power, but you would not have learned any thing useful for your future career as an attorney. Hence, the difference between passing law classes and becoming a good attorney).
My old company had a similar arrangement like yours. (many old companies had similar arrangement like yours, Motorola, Apple, Intel, all had some type of Engineer to Patent Attorney program, where they paid for the law school tuition and books). I got 1/2 of my law school paid for, before they cancelled the program. (Hence, the downside, no guarantees.)
I'm not suggesting that your company might do the same to you. But you should be prepared for the possibility. Once you go into law school, you will feel committed after about 2 years. Then, it will be difficult for you to consider turning back to your old job. (Worse part, your supervisors will expect that you will be leaving their team. Trust me, near the end of your law school, it might even feel a little like they couldn't wait to get rid of you. It might just be me).
For pay expectation, I assume you are talking about a corporate patent counsel position? Generally, if you are starting in your company right after law school, with ZERO experiences, you might get $100K per year. After 2-5 years, you might get $120K. Depending on the company. That might sound a little low, considering that 1st year patent attorneys are getting around $140K per year, but corporate patent counsels generally work 9-5 schedules and don't have much of a billing system to deal with.
That said, Corporate counsels are technically on call 24x7, with no over time, and you will have to deal with annoying "performance reviews".