He had extreme difficulty getting hold of the ingredients?
What does it mean? Did he get hold of the ingredients finally?
It's not really possible, from that sentence alone, to know whether or not he managed to get the ingredients.
It is likely that he did, at least, get some of the ingredients based on how such a sentence is usually used by native speakers, but context is needed to elucidate exactly how successful he actually was.
In terms of meaning, have and difficulty collocate quite frequently in English.
We often have difficultly and it means, quite simply, to experience difficulty.
The sentence is obviously using this collocation (with the adjective extreme modifying difficulty) in the past tense.
He had difficulty = at some point in the past he experienced difficulty.