Is it a fully detachable Goretex liner worn inside the jacket? If so, it might be cheaper to replace it with any Goretex, or equivalent, jacket of the right size.
I’d be skeptical of such a claim. The Goretex membrane, the bit which provides the waterproofness, is laminated on at manufacture. It can not be re-applied. When these membranes fail it is usually caused by abrasion wearing the membrane away. If they are going to cut out the damaged bit(s) and sew new (Goretex) patches on, their seams will have to be taped for waterproofness. The taping machines cost thousands (I used to work for an outdoor equipment manufacturer). If not taped, the seams will leak.