Well most of the work will be setting up the environment, getting infos on how to do things and depending on your game complexity, you’ll have some more or less deep changes to do.
Shaders were absolutely nothing of a problem on my side. The only thing i did was limiting a bit some computations to give a bit of relief to the console.
You could be lucky and have things set up in a few days, but I gave you a reasonable timeline for a complex game.
On my side I had to rewrote a lot of things to comply to the monogame console branch, discard external libs ( json.net might be of a problem for you ), optimizing a lot of things that i took for granted on PC, and dealing with native code. You’ll have to deal with very scarce documentation, most of the knowledge being transmitted by chat from individuals having the same problems as you.
It’s not that things are very complex, there is just a lot to do when jumping into the battle.