)Can replacing gaskets on a fridge, freezer and dishwasher be done DIY? (Not very handy)
Absolutely. My freezer door had about 25 screws that were hidden inside the gasket around the perimeter. It was just a matter of unscrewing, replacing, and screwing back again.
Sounds like the switch which is by the door of the Dryer needs to be replaced! (the switch which senses when the dryer door is shut! )
Before you replace the switch, does the dryer door shut perfectly? Maybe it is being jiggled out of place. Are there any black dots where the door grinds against the machine when closing it? It could be bent a bit out of shape (like if heavy things were kept on top).