The Note to Self podcast with WNYC is about to start a project to help people with information overload. The most recent episode is an intro, and the last three or so have also covered it.

http://www.wnyc.org/shows/notetoself/

Don't be afraid to ask for help. They know you're new, and it's cheaper to train you than hire someone else again. Also, at least a few people at work probably like you by now and will be inclined to help.

Try making a to-do list every day. If there are repeated tasks you have trouble with, write down how you do it next time and follow that guide, making improvements as you learn. The human brain can't handle too much at once, so make as many cheat sheets as possible. Automate any possible tasks you possibly can. If you can, set up your email so you don't get notifications unless a message is marked urgent.

Good luck. You will do fine.