No you can just walk in, but you should check out the cleanliness and ratings of the shop, before you decide to go 'under the needle.
Yes you need to make an appointment to consult with your artist about what you want Then they will draw up your design and get back to you with a booking Normally there is a booking fee in advanced Its usually around £50 deposit.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.