Arrghhhhhhhhhhhhhhhhhhhhhhhh my gearbox?

i have a corsa 53 reg and the gearbox is doing my head in it will never go in to first gear and it jumps out all the time. i have really ram it hard to get it in and stay then i can not get it out. the worst bit is at lights when i have to go into first gear i get all embarred cos i think pepole think i carnt drive when i can its my bloody car. i got it from gmd and i have just been along and book it in for a service which is gonna cost me �130 quid i hope they bloming fix it. it have a two year warranty on the car and this is its first service . has any1 eles had problem with theres. thanks