Quick answer is yes, you will need to buy new shifters, derailleurs, and chain if you buy a 2x10 cassette and crankset combination.
I believe you COULD temporarily buy a 2x10 Crankset and run a 9 speed rear cassette, derailluer, and chain on it for a temporary 2x9 depending on your setup or maybe a 10 speed cassette, rear derailleur, rear shifter, and chain, and play with the chainrings up front for 3x10 or 2x10 with bash. (this could be temporary until you have the cash to finish it up.)
People with more experience feel free to correct me if I am incorrect on these temp setups.
Also, be careful on the BB setup you need for your cranks, the cage size you need for rear derailleur, and the front mount/cable pull setup you need for the FD. There are dozens of mindboggling combinations of specs for the switch.
I personally switched to 2x10, and found i didn't need the whole range for our local trails, so just ended up doing 1x10. This would be a lot cheaper overall, as you have one less derailleur, shifter, and CR to worry about.