Immobilizer water proof case Questions

[Birkinboy]

Last year had to replace wet immobilizer, Porsche got me bad, $1700. Carpet is damp again. Paid Porsche to clean drains but they did not. Watched install video of case on Specialized ECU Repair site. Looks simple enuf but have a question regarding install. They did not disco the battery. Did not on my wifes Bimmer once, bag light came on removing seat, won't do that again. I always do it now no matter which car I'm working on. Should it be done as an add'l precaution or should be left alone? My 4C info says to wait 30 mins. once disc'd before doing things with electrics. Not sure about my Exige but do it anyways. I'm new to Forum but not Porsches. Wife has an '06 986 with '05 build date and also have a '75 914 that I'm probably gonna sell due to lack of storage space. Offered it to my son as a gift, likes his Civic better. What is it with this new generation? I'm a newbie to this forum, lots of great info.