stuck in 2wd :(

hey everyone

i recently took my 03 td hilux to a mechanic as she was up for her 150 000km service. while it already required a new timing belt, i was getting poor economy so i opted for a injector reco which has worked a treat, getting around 550km per tank instead of 450 :) :)
anyways, driving around on the weekend, i decided to go for a little dirt road driving only to find as i hit the 4wd button, nothing happened... i promptly pushed the gear stick into lowrange and i got jack again..

its a pain in the arse because it was working perfectly until i took it to the mechanic. after confronting him about what had happened, he said he was having trouble taking it out of 4wd and said to get it out, he had one bloke inside the car switching the button on and off, while another was underneath hitting whatever with a hammer until it came out..

now i have 2 problems. the first being i have no idea what the problem is
and secondly im only an apprentice carpenter which means i cant throw my hard earned at searching for a fix, especially because im still paying it off!

look, im at a loss at the moment and any help would be greatly appreciated