Sometimes there is some colored sealent put on the screws that seal the ecu. If the sealent is broken then yer ECU has been opened before.
Like vrsik said watch out for static. Itll fry an ecu! Also, Im not too sure about mkIV ecus, but if installing the new chip requires soldering, I wouldnt recommend doing it yerself unless yer good with the soldering gun.
jaco i had no time to talk to you at the meet but congradulation
your instaling this babe in your mk4?
ive seen your car from close and its very nice and pimping(4 door)