VBA to assign a group/household number to similar invoice customers

I have a file of ~40,000 unique invoices, which I need to group by customer name. The file is made of following fields:
Invoice Number
First Name
Last Name
Mailing Address
City
Zip

I need to accomplish two parts to this process:

(1) The first step is to identify similar customers and update Mailing Address, if required. A similar address is all three fields being equal: 1 - Last Name (exact match) 2 - Mailing address (exact match of first 5 characters only) 3 - Zip Code (exact match). If an exact match is found, then update address, if required. As an example, two invoices are as follows:

Invoice 1 Last: Smith
Invoice 1 Address: 123 Smith Avenue
Invoice 1 Zip: 10021

Invoice 2 Last: Smith
Invoice 2 Address: 123 Smith Ave
Invoice 2 Zip: 10021

In this case, change address for Invoice 2 from 123 Smith Ave to 123 Smith Avenue

(2) the second step is to assign a group number. To continue above example, both Invoice 1 and Invoice 2 are assigned to Group Number 1.

Once all similar records have been updated for one group, then move on to next group and so on. Attached is small sample of data with expected/desired results (column I and J). Thanks