I'm ASSUMING the 12F683 and 12F609 are the same for GPIO and TRISIO commands. I'm also ASSUMING you can't tell a whole GPIO to turn on or off like you did with "high GPIO".

That being said your program should look like:

cmcon0 = 7 'turns comparators off
ansel = 0 'all ports digital
adcon0 = 0 ' adc off
trisio = %001000 ' all out except GPIO.3

define osc 8
osccon = %01110111 ' you need to check this but I'm pretty sure it's right to set up a stable 8 MHz internal oscillator

MAIN_LOOP:
high GPIO.2 'if LED is on GPIO.2
pause 1000
low GPIO.2
pause 1000
goto main_loop

If you look in the PBP2.6 manual it spells some more stuff out. They either forgot it in PBP3.0 or decided to keep you guessing.

Best Wishes