How can I remove the pedals from my mountain bike?

I have decided to use a mountain bike I had when I was younger which was last used in about 2006 I have sorted out most of the bits so it is usable but the pedals have ceased and I want to put new ones on but can't get to the nut on each one with a spanner as stuff as been put against it when it was kept in the garage at my parents house so the pedals have now been pushed towards the crank so how can i remove them to put new ones on.Can anyone give me any suggestions