DC80? I think she means DC08 lol.
They are good popular machines, I bet it's the filter that's clogged. They are worth the usual mid range Dyson amount, let's say if you refurb it to look as new and hardly used, has all tools etc you can get a worthwhile amount, like between £70 and £120 if you decide to get tools for it.
If you want to sell it without the tools then you can still sell it for over £50.