Hey, I'd suggest to move your "appointment". Either you will be still strung out from the trip or you will be sleepy and slow from the Diazepam. The latter depends on the dosage but Valium would be the better choice compared to Hydrocodone since Benzodiazepines can cancel part of the LSD effects.
Next time make sure you dont have anything to do the next day. This kind of stuff just brainfucks you on hallucinogenics.
I hope you had a nice trip nonetheless.