Tom, before you buy the chemistry I would greatly recommend you buy at least the Sullivan/Weese or Arentz's book. As far as complexity there is nothing to it, but I can safely say your first few prints will not be what you expect.
As to 400 TMX, if you want the same tonality as tri X, use a green of light blue filter, depending on how much sky you have, of course with skies showing use the green filter, with no skies, use the blue. I like Tmx so much because of its versatility and reciprocity, but like you, I like the tonality of Tri X a lot more, this is why I try to use the filters I mention, to bring back a little of that Tri X feeling.
Jorge, specifically which filters do you use and what filter factor do you apply?