The drilling seems to be somewhere between the "collector" and the "bidder", maybe the extractor will be found in the package or by the "consignee". If the extractor is not found, a new one is less problematic than if the receiver really is cracked. If it is cracked, I know of no repair that would be accepted by a proof house. I wouldn't 't pass it up based on a possible crack, without a definitive check and agreement to return it if cracked. As far as lining the barrel is concerned, it may be better to just make a new one, keeping the old one for originality (John Laborde's excellent photos indicate it would be doable by an experienced American gunsmith). If either a new barrel or liner is installed, I recommend 8x57IRS because it is an excellent cartridge while generating less pressure than some of the other choices.
Mike