So actually, you want to download the updates on one computer and apply them to another?
You can install many packages at once no problem with the command line dpkg utility. If you downloaded the updates using the same version of Ubuntu, then you will find the packages in the APT cache directory.
As for a pretty Service Pack, such a thing would be impossible - there are literally thousands of software packages in the Ubuntu repositories and gathering updates for every one of them would be pointless. You can consider the next version of Ubuntu (they come twice a year, whoich is way better than anything Microsoft can do) as a "Service Pack" that you can apply to your previous version.
The easiest way would be to use network shares (Samba). This way both the guest and the parent can keep running. If you shut down the guest, then you can mount the disk image in parent and access the "drive" directly. Another way would be to set up the guest to use a disk partition from the parent. Mind you, accessing that partition simultaneously from both OSes means disaster.
