I need help with three formulas. if anyone can help.

formula 1
Need a formula that says, if a cell in sheet1 has number greater than 0,
then put €œYes€� in sheet2 otherwise null

formula 2
Need a formula that says if field is a, then put b, else carry data in a
column

Ei:
A B
C C
D D
A B

formula 3
Need a formula that says if cell = boat, then go to sheet2 and pull data.

thanks,
JaneS