Hi, Im a new boat owner, and my boat has a Volvo Penta 7.4 gi with DP drive in it. I am trying to tackle as much maintenance as i can, and i was hoping to get a little help on the following items:

1) I cant seem to find any videos on changing the impeller on this engine. I can find Volvo 5.7 and 7.4 GL how-to's, but cant find anything on the 7.4 gi. Anyone have a walkthrough, or could give me some tips on replacing?
2) My owner's manual says that to change the lower unit gear oil, i just need to remove a plug near the bottom, remove one on the top and let the oil drain out. But, a mechanic claims i need to remove the prop in order to remove the old oil. Again, I cant find much online that references this particular engine, would anyone know the proper way to change the lower unit oil?

Thanks!