Rolling pre tubes question

Hi all,
A few questions from a novice tube roller. I have a Manley Stingray II and have been playing around with the pre tubes.

1. Should amp be turned all the way off, or is stand by OK when changing tubes ?
2. Tubes that have paper labels glued on them  ( Brimar CV 4033 ) OK ?
3. Can input tubes ( 12 at7's or the Brimar CV 4033's ) be substituted for the driver tubes...6414's ? I have read that       6414 can be substituted for 12 at7's but what about visa verse ? 
 I have use the Brimar CV 4033 in the 12 at7 input  spot and enjoy the sound, so was wondering about it as a driver ?
4. What tube is more impact on the sound , input or driver ?
5. Ideas for rolling  the 6414 as i do not see many around ?

Thank you. Mike