Getting them there will be a big problem in itself, it's not as if there's a chain of friendly bases for them to use on their trip around either the Horn or the Cape of Good Hope. I'd also suspect that boats designed for the North Sea and Atlantic might be of somewhat less use in the Pacific, although I'm not sure on that - they might be ok. Even once they get there, however, they'll be thousands of miles from the nearest sources of spare parts unless they rely on the already over-stretched Japanese supply system.
There's also the question of why would the Germans do this? They badly needed their submarines to be in the North Sea and Atlantic, and would recieve absolutely no value from sending them halfway around the world.
The one thing they could send relatively easily was information, and this - in the form of designs, tactical doctrine, etc - could actually have helped the Japanese. Unfortunately by the time the Germans were in a position to do this, the time was probably past when the Japanese could have derived the most benefit from it. The logistical crunch was well and truly upon them, and even if they were capable of adopting any useful ideas and technology it's an open question as to whether these ideas would have got any attention from the IJN.
Just as an aside, you might not have noticed but on these boards anything involving a successful Sealion is likely to meet a fair degree of scepticism. This goes double if a successful Sealion is an essential precursor for the notion.