Hi and welcome.

A really good place to learn about bipolar is PsychEducation | Treating the Mood Spectrum It's written by a psychiatrist who specializes in bipolar and has tons of information.

My experience with lithium was that it made me thirsty enough I increased my fluid intake without thinking about it. I wasn't a big water drinker until lithium and even now that I've been off it for years I still drink a lot (my other meds make me thirsty). At 300 it probably won't be too bad.

Again welcome and ask anything we can help with. It's a lot to deal with when it's new.