Pin numbers being equal to BCE or GDS will depend on the parts selected, you'll have to determine that when you select your parts.Browse digikey.com,search for p-channel mosfet,look for in stock parts,FETs-Single,filter on logic level and through holeThis one looks good:http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=869-1055-ND
Goes to ground. You gotta learn some basic schematic reading dude!
Both are recognized as ground.Eagle (arduino schematics) uses a line with GND under it.
The P-MOSFET Drain or the PNP-Collector will drive the Vin of your boost/stepup regulator.Drive the circuit from whatever pin you want from the Mega - when it goes high, current will supplied to your reguator.I don't know what you're talking about with Tx and an LED.The current has to go thru something if you want to control it.Maybe switching relay on/off is what you need. Are you going to be turning this on/off/on/off quickly under software control? Or just once in a while?Anyway, that's tomorrows question, I'm off to bed. 1:30AM my time.
the package has 1 being the base 2 being the collector and 3 being the emitter.