You can probably move the old HD to your new PC and use as a second HD. Clean it all the old software and move what you want to your main HD.
Go online and look for Dell discount coupons! I saved $150 by getting additional rebates by finding Dell "special online deals." The machine I bought was great, but I would second the suggestion to upgrade to 512 mb of RAM for windows XP, only time until today I needed to open the machine to fix anything.
Don't go for the extended warranty. It's the biggest profit margin sales item for Dell, because almost all problems will be apparent immediatelywithin your 30 return period. Also, test your machine thoroughly as soon as you receive it.
For your monitor, check pricewatch.com