Question on transferring DNS zone information from ISP to Windows

We have decided to set up our own DNS servers in house using Windows 2008 R2. Our current ISP which hosts are Domain and DNS of course uses BIND. I don't think it would be that difficult to get the information from the ISP into Windows as they allow us to export the records in BIND format. I have been just copying and pasting the info into Notepad including SOA and NS records. Basically everything that is there. I then just rename the Notepad  file with a .dns extension and put it in the windows\system32\dns directory and create the zone. I point it to the file uisng the wizard and all is well.

Question I had is I need to clean up the SOA record because it has all the ISP settings as well as Serial Number. I don't know what to do with that. Its some wild number like 1334567899. I was thinking of just resetting it back to zero. Not sure what significance the Serial Number has to the current records in the zone. I thought the Serial Number was just used by the servers to determine who had the latest info.

The other option I was thinking of was to just create the zone in Windows and let it create its own SOA and NS records. Then, circle back and just copy and paste the resource records from the ISP into the new zone file and leave off the SOA and NS record. Never did it this way and just looking for some quidance. We only have 30 zones to create so no need to script it or get fancy.