Ramza,
1. It's likely just fine, but you can call Vanguard and ask to be sure.
2. $25 is 1/3 of 1%. You may make more than that in the days out of the market, or you may make less. I wouldn't pay the extra $25.
3. It should be written to Vanguard, "for the benefit", or "FBO" you. They will endorse it. Don't send an endorsed check through the mail. When you call to ask about #q, you can confirm this as well.
4. When I've done these transfers, I've just sent them regular mail. If you want you could send it with a tracking, or signature required. Really your choice.
That's my $.02 - Hope it helps.