Yup yup, did it come with tax ??
The tappets is not hard just annoying ... when i done it, it kept happening in the sapce of 3 months time, but that is not to say it will happen to you.
My experienece is that, the tappets flew out from the top, and the lock ring got smashed to pieces (it will be obvious once u took the rocker cover off).
So you will need a new lock ring (50 pence from Fiat) and a new tappet. Also what happened to mine was that the groove where the lock ring in the rocker cover was also damage, so i needed a new one of those ..
I would do as finger suggested, take the rocker cover off and if there is anything wrong with the tappets it will be obvious.
Ming