Alex,
Replaced them on my MKll a few seasons ago. I pumped vinegar from the bowl, let sit, and flushed, flushed and flushed at the pump out. Wasn't that bad of a job. Used a coupling from old hose to new hose to feed thru. As I remember the most difficult part was getting the new hose over the hose barbs, tried putting the end in hot water but ended up using a heat gun. Took 2 or 3 hours, did the pump out the day before.
It helps to add boat information to your signature. See what others have done. It helps getting the best answer. I'm sure that changing hoses on a MKl is a bit different.
Hope your project is clean and smooth.
Jim