My front lever is sucking air when I try and pull a vacuum on it with the bleed syringe.

The lever internals kit is $23 from Amazon. Is that the fix?

I bought this bike used, its a 2011 Trek Paragon, the Elixir 5's came stock. I just got the bike a few months ago. Bled and replaced pads front and rear. And now my lever is leaking.

Should I rebuild or upgrade?