excel problem

Mr. Excel,

I have a few questions about excel.

Question #1
I wanted to take a last name and a first name and combine them without having to use a new cell. Lets say that my last name is in column A and the first is in Column B. I want the end result to be in Column A with them both put together with one space in between the two,and nothing else in any other columns.
Start:
Column A Column B
Davis Shaun

End Result:
Column A
Davis Shaun

Question #2
I also wanted to use the first initial of the first name and the whole last name as one together. For example
My name is Shaun Davis...I want it to be sdavis.

Thanks for your time,

Shaun Davis