Broken spark plug

Hello I have an escort cabroilet xr3i 130 psi. I have recently been having a shuddering on acceleration so I have just replaced the spark leads but this didnt remedy it so changed the spark plugs but on doing this I have somehow broken 1 of the ceramic bits and it has fell into the engine I pulled out what I thought was all of the peices and started it up it fired up then had a cracking noise and cut out on trying to start it again it will not turn over
so if any1 that reads this has any advice on what I should do next would be appreciated
have just spoken to a friend that told me to remove the head then try to free the engine by hand and look for damge but as they are not a mechanic I am here looking for your much needed advice I just hope it aint gunna cost 2 much :(