Work advice needed

I think I will be offered a new job that I interveiwed for within the company. My boss approached me today and offered to match the pay of the new job if I didn't accept it and continued on in my current job. It would be a 25% increase in pay for the new job. I enjoy my current job, it is an obscure but vital function, I am the only one at the plant that does it. The new job would be part of 12 workers doing the same job. I have no real desire to take on the new job other than the pay factor. The new job is a night shift 12 hour swing type thing. My current job is days, m-f. If I decided to take the higher pay for my current position- do you think it would be wise? What kind of documentation should I ask for from my boss if I decided to decline the new job? I don't know if the guy can pull it off with the H.R. dept (his dad is the head of H.R. though). I just have a fear that if I decline the new job without the increase in pay written in stone, I might not get what was promised.

just like you would if you were taking a new job outside the company, or he would write if he were making an offer to someone else. The letter should mention your new salary and any other change in your status.

I have been with the company for 12 years, thats a good idea- just ask for a job offer as if it is a new job. I can then weigh both jobs on the merit of the two offers. Good sound advice Demobrat!