Sub 5508 project, might have bitten off more than I can chew!

[watchthisone2]

Hi Guys,
Been looking out for a real vintage sub for a long time and seem to have got one. Paid over the top for it as it needs a fair bit as you can see. It came from a dealer who intended to get the work done, but he never got around to sorting it.
As far as I can see, it needs as least a good service, bezel & insert, rotor post, stem, button, glass, tube, seals and maybe a fair bit more though I quite like the dial as it is. Parts I guess will be difficult to source, so would it be best sent to Rolex, Switzerland?
I am hoping that I have not been stitched up as now I have removed the bracelet, I see the serial numbers between the lugs seem too low? (400462 as far as I can see, though they are worn).
Anyway, I would appreciate any views.
Cheers,
Jeff.