Good morning
Don't worry.The Staff are quite nice and since moving to the new Library ,most don't know exactly what they are doing either,so are less intimidating.
There are 3 staff on the general enquires desk and 2 in the Reading room.
While it's not necessary to book ,I would.
I'm not sure what records you are looking for but would assume baptisms and burials for a start.Most parishes will be on microfilm ,so you will need a reader.Obviously there are a finite number and if you're traveling you don't want to get there and find they are all full.So phone then up and book.
Your sister in law will be booked in on her ticket and you will receive a guest one for the microfilm viewers.No need to join up for that.
If you have to look at original documents ,for Handsworth St Mary's for example which have not been microfilmed at that date you'll need a readers ticket and for that you'll need 2 forms of ID.One with a signature and another with an address.Ask them what they will accept while you're on the phone booking the reader.The Reading room is on the same floor,floor 4 ,but in a separate area and you will need to book a seat for that.(ps take a pencil without a rubber on the end.They are funny about that).
On open access are Electoral Registers and MI transcripts for the Birmingham parish churches.I believe the big cemeteries are on microfilm.
There are guided tours of the building ,but how much time do you have?Really it's in the front door and up the escalators straight in front of you to the fourth floor.The rest is a lending Library 0-2 and a reference and British Film institute Library on floor 3.There are toilets,photocopiers etc on each floor.If you need a break and a coffee there is a cafe area by the front door.
Don't forget that at the end of the day you are paying the Staffs wages.Be reasonable ,be polite but THEY are there to help.
Have FUN and I hope you find what you are looking for.
Ciderdrinker
ps if you really can't face it or don't get exactly what you want, most of their collection is now on Ancestry.So bear in mind if time running short go for their big Cemetery records rather than parish registers or Electoral lists which are on-line.Stuff you can't find elsewhere.