If you search around this forum, there is lots of information about reassembly. Specially made tools are available for purchase in the classified section, or you can make a tool for recoil spring reassembly out of a bent paperclip (that's what I use). There is a thread here that shows how to do it.
Get the spring perfectly centered when putting the slide back on, and you should be ok.
It's definitely a tricky gun to reassemble. With practice, it will get easier.