Changing hands on an Apollo 8 DSOTM

No. Omega has made a ton of different watches with the name Speedmaster, using many different movements (Lemania based, Valjoux 7750 based, F. Piguet based, plus the current Omega movements, etc.) so not all hands will fit all models.

It's unclear at this point if the hands from say a Cal. 1861 will fit on the Cal. 1869. Omega doesn't provide hole sizes for hands so the only way to tell is to look at the parts that the hands mount to, and of the 6 posts that hands mount to, only two are the same part number as a typical Speedmaster Pro movement, so the cannon pinion where the minute hand would fit, and the hour recording wheel where the hour recorder hand would mount. The hour wheel, fourth wheel, minute counter, and seconds counter are all specific parts to the 1869, and may have different diameters for the hand mounting.

I'm assuming you would be primarily interested in the hour and minute hands, right?

What I can say is that hour/minute hands from a regular Speedmaster Pro would be short. The hands on your watch are 10.15 mm long for the hour hand, and 14.6 mm for the minute hand. The regular Speedmaster hour and minute hands are 9.5 and 14 mm's respectively.

Cheers, Al