Effect of GL account change on Shopping carts and POs

Dear SRMers,

System Info : SRM 5.0, ECC 6.0

Our client is planning to change the GL account numbers in the COA from 21XX series to a 31XX series.

So I wanted to know the impact on a.) the Shopping carts in approval process using the old GLs and b.) for the POs that are already created using the old GL's.

Can we change the GLs for Shopping carts in approval process and for PO's already created or what may be the best approach to resolve the issue.

Points will be rewarded for answers.

Thanks in advance,

Bob