Find and replace

Hello.

I have a sheet (original part numbers) of part numbers (and descriptions, prices etc). Many of these part numbers have been changed, so I have been supplied a 2nd sheet (recode list) with the old number and the new number in 2 columns.

I need to get the old number in sheet 2 to search for search for the old number in sheet 1, and then replace it with the new number in sheet 2 - before moving to the next row and doing the same?

Please note
There may not be the same number of items in each sheet
The parts are not always listed numerically (see the red text)
I have attached 2 files for clarity.

Many thanks in advance.