Appending Updated records VS Wireless Connection

Greetings:

I am researching, what on the surface seems quite complicated and is difficult to clearly articulate but here it goes.

I have an MsAccess2000 database that resides on a laptop. When I connect to the server I have programmed a command button to run an append query that in turn moves the data to a table on the server. This limits me to only adding new records. What I would like to do it to be able to add additional information to say a memo field in a record and then when I append back to the server only the records that have been edited will be changed leaving the original data intact but adding the additional information.  

Another consideration: If I add this database to another laptop, where another user will be adding information likewise, and two users by chance update the same record, would this pose a problem that could not be managed?

I am looking into a second solution to the problem that is connecting to the server via a wireless Internet connection linking the database directly to the server. Is this practical? If what method? VPN?