The first two, I think will be the most difficult.
I can see the headset being frustrating.
The only time I removed a front derailleur I had marked its position before removal - but that's not an option for you. But lots of people do it all the time. It might take time, but it's doable.
The chain is easy enough to do. You have quicklinks? The issue is getting the correct length. Do you have a chain breaker tool?
As for the cables, a good cable cutter is vital! When I put new brakes & cables on mine, I just cut the outers to the same length as the old ones. A like for like replacement. However, I'll be redoing that job and using longer outers on the front (at the handlebars) to allow better manipulation of the cables around my handlebar bag.
My assumption is that a longer cable won't make any significant difference. If anyone has any objections to that, I'd love to know!

Thanks!