^I didn't know we had a psychic around here!
Are you going to die from 30mg diazepam and alcohol? No, mostly likely not... the real problem comes in the fact that it drastically increases the likelihood of blacking out and doing something really stupid, dangerous and/or illegal due to the disinhibition and intoxication.
If you have a higher tolerance to benzodiazepines and/or alcohol, this may not be a very big problem. If you do not, then once you start to get really intoxicated you may have the urge to keep taking more and more of either/both and further increase the likelihood of doing something stupid, dangerous and/or illegal.
This has been covered many times before as Mr. Battler alluded to so if you'd like more information, have a search around.
PM me if you have any questions and be safe.