find and replace for instance

Hello world.
I have to find and replace across multiple instances. I have the following on two sheets in one workbook.

Sheet 1
A
a1 = x
a2 = y
a3 = z
a4 = y
a5 = z

Sheet 2
A...........B
a1 = a | b1 = x
a2 = b | b2 = y
a3 = c | b3 = z

What I need to accomplish is for any time the value of B1 in sheet two is found in column A on sheet 1, that cell in column A is changed to the value in A1 on sheet 2.

So the end result of the above would be:

Sheet 1
a1 = a
a2 = b
a3 = c
a4 = b
a5 = c

If it makes things easier I can also easily put the values in Sheet 2 into sheet 1 in two empty columns.

Thanks,

NickTater

Thanks, Worked great.