Regeneration by Max Allan and Barbara Collins

Joyce Lackey was a classic baby-boomer. She had it all: a high-paying position, a beautiful condo, a BMW. But there was one thing she didn't have any more^^her youth. And that was what she needed most. Her boss fired her because he wanted someone with 'young blood,' 'young ideas.' Someone young. Joyce was forced to start all over again. But could she compete with all the beautiful young kids who were so hungry for what she had? That's where the X-Gen Agency came in. They could give Joyce everything she wanted, everything she needed^^a new job, a new body, a new identity. In short, a new life. But there was a price. A very high price. It seemed reasonable enough when Joyce signed the contracts, and besides, she was desperate. By the time she realized what she had done, it was too late to turn back. This was one contract without an escape clause