It's not complicated, trust me, I've done it so it can't be
I've re-built two '80's bikes, converting one to modern 10 speed, and built up a new frame as well.
The last frame I built I just had to get a new seatpost as the one I had was too wide, and I had to get a braze on front mech as opposed to the clamp on one that was fitted to my old bike.
What bike is it you've got, and what frame are you looking at building up?
Or, use the project as the perfect way to learn the basics of bike maintenance.Nothing in particular. I probably should learn the basics of bike maintenance first before taking on such a project.