I was reimbursed for tuition expenses for more than tuition costed me. Will I get in trouble if I use the extra cash?

Yes, it could be considered fraud, because you were paid more than you were entitled to receive, as an Illinois man found out last year when he bilked his employer out of nearly $46,000 in tuition reimbursement for an MBA degree he was not pursuing, although his company believed he was.  He plead  guilty to a felony charge of theft by deception of between $10,000 and $100,000, was given jail time, two years of probation, a $530 fine, and ordered to pay a total of $45,653.25 in restitution to his former employer.  I would suggest paying back the money, and if your company decides to press charges, enlist the help of a criminal defense attorney.