yes, buy the same connector, if it is old ide, buy ide but if it is sata you will need that
if it is a old sata and you buy a sata II, it will work, i have done that
sometimes if the hard disk is 200gbs(for example) you shouldn't buy a much larger one than 500gbs, in laptops is not uncommon to see that there only will be support for certain sizes
about brands, samsung is what is easier to find and usually the cheapest but if you can find a toshiba, it really is a good investment
does that dell laptop has a direct access bay to remove the hard disk?
if it has, all you have to do is unplug laptop, remove battery and remove the 2 or 4 screws in place
many models has a tray that has to be pulled gently in a specific direction, some others have a small screw holding in place that tray so remove it first
once you have removed the tary, remove the screws in the tray and remove the hard disk, put the new one and put everything back in place and then boot the machine, enter in the bios and see if the hard disk is detected correctly
the old one, you can put it on a external case, some really nice samsung models, you put the old hard disk, connect the case as a usb hard drive and recover the files if you couldn't do it before removing it with a recovery tool
if you format the old hard disk and doesn't make weird noises or doesn't show errors when formating, you have a new external storage device
