1. Yes, really it is kinda hit and miss though. Your best bet, is to go down to best buy and take a liveCD with you... Don't be obvious about what you're doing cuz I don't know that they would allow it, but I have done it, just put the CD/DVD in and restart. Make sure it is i386 unless you plan on using x86_64, that way you are not limited in trying it in all of them.
2. I don't even think dell really "supports" linux, unless you use their silly *buntu thing. If you want true support from them you will pay for it too. And forgetting getting fedora support ( except from us..
Watch out for nVidia MCP51 sound cards ( Nightmare ) It will show up in windows vista as a Sigmatel High Definition Audio, not that they ALL don't work, but when they don't there is not much hope. Good luck my friend, and come back to us with any questions. Have patients and remember there WILL be a learning curve.
EDIT: DO NOT BUY A GATEWAY LAPTOP FOR LINUX!!!!