You asked about parts, so here is the list:

Left shifter, if you can find it sold as a single. Would most likely need the pair.
Crank.
Maybe BB. If current crank is JIS taper, then definitely BB. If Hollowtech, then you are OK. If switching crank manufacturer, then most likely yes.
Front derailleur.
Maybe rear derailleur. If currently short cage, you will need at least a mid-cage for chain take up.
Chain should be fine, unless you go to bigger big ring on the new triple crank.
Maybe cables and maybe tape. Totally dependant on you skills in getting them off and back on. I typically plan to replace both.

Other than that, you should be fine.