Yes it's a long way but there's a free bus between the two - details here [broken link removed]
T1,2 & 3 are the original airport buildings - they're all essentially one long building I think .. T4 and T4S are the newer airport terminal which opened a few years ago - it's enormous (looks beautiful but not sure it's so well designed the amount of going up and down stairs in it seems crazy to get to your flight sometimes)
I would say it would be prudent to allow 30 mins after exiting T1 to wait for the shuttle bus, catch it over to T4 and find your bus stop for the next bus.