They're easy to do, hardly any preload on the spring so you don't need a spring press. Like matey says, try to avoid taking the safety catch out, or at least, try to remember how it came out! The other thing you need to make sure you do is to remove the trigger blade and trigger spring before you go to take the mainspring out, or the trigger spring is liable to get mashed.
A gas-ram is a quick, simple way of making them much nicer to shoot. Recoil is quicker and more manageable. The trigger is still cr@p though, but if you're gonna take it to bits you may as well polish the sears whilst your at it. Also, replace the trigger spring with a lighter one- the ones you get in ballpoint pens are often ideal.
HTH
And day by day and dauntingly, Our anger does increase. While you ruin us through ignorance,
How can we keep our peace?