Rolling pre tubes question

Jazzman, I always follow the manufacturer's suggestion. I just try to find the lowest noise version of the type. RAM Labs tests their tubes for noise and put the speck right on the box.
Any labels on the tube should be removed. I always turn the unit off before I remove tubes even if they are not that hot. You do not want any impulses getting to other equipment. If the unit is disconnected it is off anyway. 
If you really want advise from the hourse's mouth call Manley and ask.

I can’t add anything, far as advice, to what mijostyn posted, but- that Brent Jesse Recording, Upscale Audio (Kevin Deal) and Vintage Tubes Services (Andy Bouwman) are all excellent sources, for noise-tested/rated tubes and accurate information.                  Of course; Kevin Deal is also very familiar with your Manley, being a dealer.

NOT TO YELL - BUT RESPONSES IN CAPS BELOW

1. Should amp be turned all the way off, or is stand by OK when changing tubes ?  OFF ALL THE WAY ALL THE TIME
2. Tubes that have paper labels glued on them ( Brimar CV 4033 ) OK ?  BEST REMOVED, ESP FOR POWER TUBES
3. Can input tubes ( 12 at7's or the Brimar CV 4033's ) be substituted for the driver tubes...6414 ? I have read that      6414 can be substituted for 12 at7's but what about visa verse ?  SEARCH ONLINE FOR TUBE INTERCHANGEABILITY... GETS TRICKY SOMETIMES, DEPENDS NOT JUST ON THE TUBES BUT THE CIRCUIT THEY ARE WORKING IN... CHECK WITH MANUFACTURER BEST IDEA
 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 ?  INPUT TUBE MORE SENSITIVE THAN DRIVER/BUFFER IN CHANGING SQ
4. What tube is more impact on the sound , input or driver ? SEE 3
5. Ideas for rolling the 6414 as i do not see many around ?  https://audiokarma.org/forums/index.php?threads/0528-6414-12au7-equivalent.493894/

If you have a preamp where you need to remove the cover to access the tubes you need it to be off (and best unplugged) for about 30 minutes first before rolling tubes to insure hazardous voltages in the power supply have had time to discharge. Not matter what you should NEVER change a tube w/o powering down first. 

Here is an explanation for the paper labels from the Tubemonger’s website, except your labels were printed, not handwritten. I would remove them if you can:

*Each tube came with two factory stickers (click Larger Photo). A hand written individual serial number, and a handwritten number PM25525-1. Tube boxes also have a sticker with printed number PM25525-1. Tubes were factory tested and serialized for some qualification (PM25525-1), except we don’t have specific details of the qualification.

The input tube will have more impact on the sound, but both can have an effect.

It appears that the 6414 is a variant of the CV4033/12AT7 according to the Brent Jessee website, but it’s always best to check with the manufacturer before substituting. They may also recommend brands of tubes to try. Most manufacturers are happy to answer these types of questions.

6414:An industrial, computer rated dual triode,virtually the same specs as the E180CC or 7062 listed above. Unlike the E180CC, this tube was made in the USA. It is a more rugged build, with the Raytheon blackplate type sporting triple mica and military ratings. This tube is also like a 12AV7 and will work wonders in any 12AT7 spot, and may be just the ticket if you want to boost the gain of a 12AU7 circuit. The 6414 is getting very hard to find, but with a 10,000 hour heater rating you may never need a replacement. Discussion groups rate this type very highly for use in headphone amps. Stands about 1/2 inch taller than the standard 12AT7.6829:

Yeah I had the E180CC = 6414 in my LS9 Jadis Clone line stage, ( sold 3 weeks ago),, and honestly, I found no  sonic gains. 
Unit came with EH12AT7's,. I  also ran Siemens 12AT7's,, and  found no sonic gains. 
Honestly as others mention, if the unit comes with AT7's, stay with AT7's. 
The budget priced 12AT7's will sound no dif from the high priced Tele 12AT7's. 
The 12AT7 is a great pre tube, as it is so neutral sounding, = delivers the music cleanly, w/o distortions. , so stay with that tube as the designer made the circuit for exactly that tube. =  The amp will be more happy, = no disruptions down the road. Play it smart. 
If you are looking to make  tweaks try employing new capacitors, like silver or copper. 

When changing tubes turn everything off.I never heard of a tube with paper on it thats not good.Some of the best sounding tubes(6922) are Amperex.

I never heard of a tube with paper on it

https://www.tubemonger.com/Brimar_CV4033_NOS_1960_62_Prem_CV4024_STC_Eng_FAC_p/2042m.htm

Yep, that's them. They do sound ( to my ears) a bit more alive and dynamic then the ...12 at7's.