I hate my job (Computing) :( ?

Hey guys i really badly wanted a job as something practical say a car mechanic, plumber, joiner etc.. but my mums friend from next door offered me a job as an IT something behind a computer manifesting and stuff, its 9 pound an hour and i have done it for 2 weeks this friday, this past week and a bit has felt like a month.. i sit bored with nothing to do the work is a bore as i was never a computer type guy unless im at home on the internet, spreadsheets is just not my thing.. i walked out that place for a walk at lunch only to see my friend doing his welding which looked so fun he loves it, yes i know the pay in an office job is alot more pay than a practical job, and in the winter its cold outside.. Im 18 years old and the job is currently 3 months temporary which they say they will keep me on after it if i do well, but the thing is i don't wanna stay on, i wanna save that money i make after teh 3 months (4000 pound) and move onto a new life or something, i would feel bad considering he put his reputation on the line and wasted his time trying to train me that 3 months then i just quit, or if i quit now.. hes a nice guy and all its just i really am not a computer guy i sit there watching the clock, watching people outside in boiler suits getting dirty and living life, watching forklift drivers near by, just wishing i was them, what can i say to get away from this place? should i do the 3 months then stay.. is it normal to be more of a practical guy rather than an office? is money everything im only a teen and my parents wont throw me out they just helped out.. i think maybe 3 months here save the money go for a mechanic job, i just really need help, i can't see my self in 5 years still at this job, to be honest i can't even see 3 months.. i feel like a **** if i click, but i guess i am what i am and nothing can change me.