How can I make a DC to DC step down voltager regulator?

I want to make my own BEC (battery elimination circuit) for my RC helicopter, so that I don't have to spend $50 and buy one. I'm also very impatient when it coming to waiting for things to arrive in the mail. I have some basic electronic parts.  I have some N-channel MOSFETs, Diodes, Resistors, OP-amps, and comparators, A butt load of Capacitors, My helicopters ESC(electronic speed controller) uses a 11.1v Lithium Polymer(LiPo) battery, but my RC receiver can only handle 6volts Maximum, at about 2-3Amps. I don't have any wheels, so I can't exactly run out to my nearest RadioShack to buy an LM317 voltage regulator. so I'm here to ask if anyone knokw how to build a [step dowm voltage regulator] from basic components?

Schematics ,and parts list would be appreciated. I have no idea how much current the LiPo battery is pushing, it exceeds the max range of my Multimeter which is 10Amps. fried couple of diodes, and blew the fuses it trying to measure the raw current. I need help please.

Hey, um, if it's not too much trouble, could you please post a link to the too-expensive power converter that you don't want to buy.  I mean just so those attempting to answer this question could take a look at the thing for which you want you want a cheaper substitute for.
You don't EVER measure current by shorting the battery with a meter. If it has to be done, its done with specially made test equipment that can draw a pulse for a few microseconds. LiPo batteries really don't like being shorted either.

You'd be better with a switching regulator, rather than a linear one - 6 v@3A, means you'll be wasting 18W in the reg.

You'd be better waiting for your order to appear.
+1. Helicopters are very failure prone and you'll only get one chance to make it right.