Those are some good suggestion but some people do like alcohol with their opiates. Sure snorting that much powder may be a bitch but if he wants to go for it let him. Just one note, some people have claimed that snorting all that powder actually interferes with absorbtion lowering instead of raising the amount absorbed. No sources or convincing ancedotal accounts though so it could be BS.
As for the tylenol this has been addresed countless times in this forum and health Q&A. Zorn did a really good summary of this issue with journal refs for pretty much everything.
The short answer, assuming you do NOT have a preexisting liver condition, is that it takes something like 4grams of tylenol combined with drinking a day to start causing serious problems. If this is like a one shot deal I would hardly worry about it, the respitory depression of alcohol and opiates would probably kill you before you ate enough percs to cause serious damage.