I have an 06 1.4tdi fabia but the miles are very high and I want to swap the engine to a pd100 engine could anyone give me some info on it 

It will be quicker and cheaper to just sell the 1.4 and buy a 1.9 instead, there are too many differences to make it viable.

The days of easy engine swaps are long gone, mainly due to module coding and mapping.

Seconded

As above - what is your definition of high mileage, my old 1.4TDI now owned by someone else has just been MOT'd at 177.888 miles.

No point in doing so. You'll end up with a modified vehicle fewer people might want to buy later and very much more limited and expensive insurance options.

 

Either make the best of it or sell it and get a 1.9TDi.