Upgrading my Groupset

Hi!

I have a Trek Domane AL2 that I've had for about 4 years. I love the bike but the Claris 8 speed is getting limiting now and I struggle to find an easy cadence on flats because of the jumps between gears. I've signed up for a 70.3 next year and I want to upgrade but I don't have new bike money.

Basically what I'm looking at is putting a 105 mechanical 11 speed group set on my current bike. The freehub will take it because Trek use the same frame and Bontrager wheels for the higher range models that come with 11 speed. So I figure I'll just need levers, derailleur, chain, and cassette to make it work because the levers will pull the mechanical disk callipers I already have and my chainring should still work. Obviously I can spend more to add more but that's what I think I'd need at a minimum.

So I have two questions really:

1. Will this actually work?

And

2. How much difference will this upgrade actually make?