The bolts aren't the problem. The interface to the vehicle electronics is the problem.
And the question that someone has to ask ... Why do you want to do this? If you want a Jetta with the new engine in it, complete with warranty, just trade in what you have for a complete 2015 model car. If you want a Mk5 with the common-rail engine, you already have one. If you want a Mk5 with a bit more power, just chip-tune what you have. If you're worried about the HPFP blowing up ... you are in the USA, where VW has been covering these to quite high mileage. The new engine is too new to know whether it will really be better, or if it will just trade off some known issues for some unknowns. Sometimes it's just better to deal with the devil you know ...