Generally the Recovery and Diagnostics are tied to the factory install, but Dell's have a bit more independence. So you can try them since you want to keep the factory installed Windows 7 for the time being.
Welcome to Clean Reinstall, something which tech enthusiasts do first when acquiring a factory-bloated computer. While your second partition install might not have all of the vim than if you'd completely format the drive first, you should get a good comparison and have the factory install to fall back on if needed.
First I would make the recovery disks so you have them in case the Recov is disabled by the second partition install. You can also make a Windows 7 backup image of your entire HDD saved externally to reimage HD easily in 15 minutes.
You can pull any drivers not in the installer or given via Windows Updates by browsing in Device Manager to windows/system32/drivers and /driverstore files in the factory install.
Other apps can be gotten from the Dell website Support Downloads page for your model. Dell might also have provided you with an apps CD which is even better.
You will need Adobe reader/flash and Java runtime from their websites. Java has a free compatible Ofc suite to replace Works.
Create the second primary partition formatted NTFS in Disk Management, boot from the DVD using Custom Advanced drive tools to format once again before install. Select "connect to internet during install" and keep ethernet plugged to get latest drivers/updates during install.