pekay,
If there is any question as to the hours you logged after that first 8 years you might consider asking the company for a printout.
Yes, you will show both your original logbook and your computer records. Remember, this is your diary, your word. They need to be able to do some cross-checking just to be sure you are what you present. Can they read and understand what you are logging?
Professional enough is subjective. Would you be impressed if someone handed it to you?
Hope this helps.
PS - don't forget to sign each page of your computerized logbook! (sorry....)