Re the re-installation of GRUB, I found this solution great.
The site takes you through the steps to install Boot repair from your live boot, and this is quite smooth. I've used it a couple of times messing around with my home PC - wife and kids were thrilled to bits when they got their installation back :)
Re docs and other settings, I have found a nifty way to future-proof this. Learned it from a friend.
When you partition the system for installing windows,(or even just for Ubuntu) keep
(1) a 15 GB partition separately for the system folder "/" ,
(2) A separate partition equal to 2-times-the RAM for SWAP, and
(3) A separate "/home" partition. This way, whenever you want to update your Ubuntu version, all you need to do while installing, is to select "something else" during the partitioning process. Mark this 15 GB and format as Ext4, use this partition as "/". Mark this partition to be formatted.
Now is the best part.
Mark the existing /home partition that you are already using to be mounted as "/home" but DO NOT FORMAT IT. (that is, don't check the "format" box)
Make sure that you give the existing user name and password when installing the new version . This way, once you reinstall,your system will be installed (old one will be deleted, of course) and your entire home folder will remain as it is. Not only that, much to my pleasant surprise, even my addons, bookmarks, saved passwords - everything was fully intact.
You will need to however, update the software, and reinstall all the other software / packages that you want, once again , since the new one will not be compatible.
You could also try to google for "aptoncd" which is a programme used to backup your existing installation packages, and this can be re-installed on your other computer (or friend's Comp) running the same version of Ubuntu so you don't need to download the packages each time. You will have to select these packages from the Ubuntu Software Centre. It will not download these packages.
Hope this helps - at least for the future.
(I did exactly this - had to go back to 12.04 after installing 12.10)