Changes in Asset(wrong assignment of Account Determination)

Hello Experts

We have implemented SAP in Jan11, & uploaded asset as on 31.12.10.

It come to notice that some asset uploaded with wrong account determination(as they are Machinery construction Equipment but assign to the GL machinery office equipment,account determination wrongly assign to that asset class).we come to know this when we retire some of that asset as posting happens in office equipment GL.

Now how to rectify all this posting?

1)if i made the changes in account determination it only applicable for new asset creation but what to do with all the asset previously uploaded? may i delete it & reload the same with correct assignment?

2)Depreciation run not yet happen,how to handle it for this wrong asset data?

3)What are the other impacts it made in systems which i need to take care?