I am also about due for this same job on our '05 400. I have not done it yet, but I have a plan and I have done a lot (way too much) work on the head system on our boat so I know a few things that may help you out.
Also, there is some info on this exact job in another current thread called "hose replacement" it may be helpful to you as well. Here is a link:
https://www.trawlerforum.com/forums/s11/hose-replacement-39537.html
1. Yes, you need to take the toilet out to access the head end of the hose. It is attached to the bottom of the toilet on what VF calls the "funnel." I had to replace the funnel on my toilet, so I am familiar with the set up. There is probably not much play in the hose under the toilet, but after I disconnected the VF end from the VF generator I was able pull the hose toward the toilet about a foot. I am hoping that this means the hose is not zip tied in so tight that it won't slide.
2. Remove the entire VF generator unit (flush it quite a few times first) to get it out of the way. It's easy, just take off the inlet hose, which is on the fwd end in your pic, and the outlet hose. Then disconnect the wires, of which there are only two. Then remove the four screws holding it down and pull out the unit.
After it is out you will have good access to the aft end of the hose.
From here, all I have is a rough plan. I hope to be able to glue the new hose to the old hose with a double male adapter, grease up the new hose and use the old one to pull it through. I think pulling the hose from the head into the storage area under the helm will be easier, but I am not sure about that.
In the other thread, Mermaid said her boat has an access plate under the sink in the head, which may allow you to reach some, or all, of the zip ties if the hose won't pull through. My boat does not have this plate, but it would be a good spot to cut one if needed.
If that doesn't work, maybe an access plate in the bulkhead under the helm?
Please post and let us know how this job goes for you.
Thanks and good luck.
Doug