Replacing fan with Nutone Fan-Light 763RLN
The original power source is simply a black and white wire, the new fan has 2 white, a black and a blue.
Do I simply just connect the whites to white and the Black and Blue to Black ?

What do the wiring instructions that came with the fan tell you to do?

If you do not have the, let me know and I can see if the instructions are on the Nu-tone web site.

Your current set up has but one circuit running to the ceiling box. If you connect the Nutone up both the fan and the light will always be on at the same time, you OK with that? Normally we would install another switch and pull another hot line to the ceiling, is this possible for you? If not, Connect all the whites together, those are your neutrals. Bring all black and blues together and twist and wire nut them securely.