Replace function

Replace function

I have a field called post code

I want to do 2 things

1.

If the user inputs the post code as DA81HG or DA116DF

I want to convert these to DA8 1HG and DA11 6DF

2.

I want to be able to convert DA8 1HG to DA8+1HG for google map purposes.

Cheers for any help.