Experience with AMR DP-777

Hi there, I'm fairly new to audiogon, but have been assembling high-end systems for about 15 years now. Recently bought an AMR DP-777 and swapped tubes and it killed my left channel the first time. I'm no stranger to swapping tubes (in DAC's and Preamps), so I was surprised this happened. I've read some other threads that this sort of stuff has been an issue with this DAC. Of course the DAC sounds, but I have two questions/points:

1) for those of you that have experience rolling tubes with this DAC, what is your procedure to make sure it does cause some any system failure with the unit?

2) second thing is I've sent the unit in for the SE upgrade and will be able to report back to you guys the difference/improvement in sound, as I know it's sonic signature very well
I would be very interested in your perceptions regaurding the upgraded DP 777. I am considering the SE update as well. Would like to hear from folks who have gone the SE route.

I have no experience rolling tubes in the AMR. There is a long thread on Computer Audiophile that discusses this DAC and similar results concerning tube rolling, among other things.
I used to own the AMR. I would be careful rolling tubes with it. I would advise contacting the manufacturer first. They had design problems early on. I have no idea if these problems have been addressed. At the time the maker had a caveat not to roll tubes at all. I used to own the AMR.