seat arosa throttle not working

hi all thanks for the add,i have a seat arosa 1400 which has developed a fault,lost the throttle control . a mate said it could be the throttle pedal position sensor.how easy a job to do,where can i get one from,he also said code 1639 and 342 came up? please help any info muchly appreciated.thanks again

nice to know people will help you.think i will put into garage for help.......cheers