Background
I've been holding my current position as a Software Engineer for almost 6 years now, during which I've participated in many projects.
Most of the projects were rather small scaled, but there are 2 major projects that were started from scratch, which were mostly designed and implemented by myself. I think I can say that I have a lot of responsibility on my shoulders (as a Software engineer, mostly) as these products were sold (and are currently being sold) to our customers.
So I got a call last week from a very successfull high-tech company saying they have a job offer for me. After 3 interviews I got a phone call from HR saying they're going to hire me, detailing with salary and extras.
I still need to take a psychophysiological detection of deception examination, but it shouldn't be a problem to pass that exam, and I'll be probably signing a contract next week.
The dilemma
My current employer knows nothing about this. I need to give a 30 days notice before I leave but I am afraid that it won't be enough for them to actually find someone in time, since there's much to learn.
I do care a lot for the company I currently work for, it's like a 2nd home to me.
Should I talk to my boss and notify him of these events, saying I'll be probably leaving in a month or so, or, should I wait until I actually sign a contract with the new company, before saying anything?