DRT400 Fan Replacement

I just noticed our main Tivo unit, DRT400, has gotten pretty loud. First thing I'll check tomorrow is the fan, and if that's the culprit and for some reason a simple cleaning doesn't resolve it, is there any reason I can't buy an off-the-shelf 120mm fan to replace the faulty fan?

$19 plus S&H handling for a fan seems a little inflated. I also have a TCD649080 Unit that's dead (got fried in a T-Storm) unfortunately. Same fan? Can I cannibalise it for use in the Humax?

Thanks!