Revising Chart of Accounts

My company's Chart of Accounts has not been reviewed for a number of years.  I would like to make some changes to its structure to bring it in line with an industry standard. 

I understand I can easily change Account Name details.

Can I also change Account Numbers? 

Would these bring forward the past transactions that have been allocated to this account? 

Would the old Account Number become available again?

For example:  Currently have "6-0030 Board Expenses".  I would like to change this to "6-0085 Board Expenses"

Looking for answers to my questions above.

Thanks!