Also, your own character's party skill levels will add a bonus for your companions. At 2-4 points there's a +1 bonus, which becomes +2 at ranks 5-7 (or maybe it's 5-8? I can't remember). The bonus also applies to your own skill, so if your surgery is at 3 when your medic companion is knocked out you'll still get an effective skill of 4 from your own character (3 base points and 1 bonus point). I think it's pretty much always worth it to either put 2 points into surgery, or just 1 plus the surgery skill book; the bonus for your companions' skill is handy, and it gives you a little bit of a backup to fall back on if they go down.