Hello Srinivasan,
1. Equipment Description
There wont' be any adverse impact. All reports queried on on present or past dates (like IW28, IW38, IH08 etc) will be presented with new Description.
2. Spare parts
I assume your query is about the BOM list. Here too I do not see any adverse impact. You will be presented this new BOM if you are taking help of List option while taking components into Order. Previous Orders done so, would not have any changes, they will be with the same old components, even these are removed from the BOM list of the Equipment, on which the Order was created. And updating these BOM lists is not an uncommon activity. For example: A code for same spare part might need a new code while fresh procurement due to some business compulsions. I have seen such cases where same spare part is available with two code. These are the scenarios which we need not worry while or listing /updating a BOM.
This is my opinion through my experience so far.
Best of Luck
KJogeswaraRao