I got a crusty brake booster (with pics) is it junk?

[darkone]

hey all, i bought this from a dude yesterday, why i didnt flip the tab and check the res i dont know, but today i did, and its pretty crusty in there. is this thing worth saving? i already spent the dollars on it and a trip to get another one is gonna be min. $50.... any advice on how to deal would me much appreciated. thanks.... =/

ps, this is what ive got for my brake system. do i need any other hardware?? im not sure what this little valve on the side is?