There are three particles that are pronounced differently from the way they are written:
は, pronounced わ;
を, pronounced お;
へ, pronounced え. This is only for particles.
The "え" in "namae" is not a particle, so it remains なまえ.
For your other question, by using a specific time with the まで particle, the meaning is implied; "closes at six" isn't the direct translation, but that's what it means. If you wanted to specify that the store closes at six, it would be 6時に閉店します。