i graduated with pass -cgpa 2.47/5.0 scale mechanical engr higher national diploma.i am working presently as a mechanical engineer in a manufacturing company with 8yrs experience.i took a big risk by doctoring my result to lower credit b4 i could get this job.someone wants to offer me another job now worth 120,000 per month.i dont want to take another risk again.because im even thinking of resigning from d job.kindly advice me on what to do.should i take the risk again or i should apply with my pass plus d 8yrs experience.

Only a devil will ask you to continue using the certificate.
Who knows may be it is your intuition telling you to stop before you get caught.
No one with a moral conviction will say you should apply for the new job and then continue with the old one. It is a sin and a crime.

However, if the tables were turn around and I was in your shoes, it will be very difficult to resist the new offer.
120k is a lot of cash in this present struggling economy.

My advice is that you establish yourself and be a consultant and hustle your way to success ASAP.
Not an easy thing to achieve but it's better than using fake certificates all around.
With the kind of course you studied and with 8 years There is no limit to what you can achieve in life.