Oh No guess who squashed the heater o Rings

Gentlemen advice please it appears the swimming pool I now have in the driver footwell is due to me squashing/disturbing the o rings in the heater. Am I going to have to go in and change them? Or is there a quick fix - they were alright before I changed the engine?
Also I have picked up an idea from somewhere that the duct that is in the way can be cut to make access easier and taped back with hevac tape - anybody tried this?
Any help much appreciated
cheers
Sandy

Often its a short time after LPG has been fitted that the o rings leak,as a result of the heater pipes being disturbed when cutting them to tee in the vaporiser pipes.So changing or removing your engine can have the same effect.There is no need to cut any heater ducts,just remove the rh upper and lower panels and the Hevac panel.Then a very long screwdriverto undo the screw and you are away.Make a funnel out of carboard to send the coolant into a bowl,to avoid an even wetter carpet.Did one on Friday,the screw was undone and the o rings were new - but leaking as they werent clamped properly.Took just over an hour for the whole job,but I have done it lots of times and if the screw wont come undone the it is big trouble.

All done and thanks for the info took 2hrs which is not bad as i didnt know what i was doing.
Thanks again