I'm a mohs tech for a dermatologist/dermatopathologist in Florida. I'm the one who calls patients with results so I guess you could say I'm an expert on this particular subject. One to two weeks is average for skin biopsies - even it is cancer. If a specimen turns out to be something urgent, the lab will call the doctor directly and give them a heads up even before the paperwork is finalized.
As for the probability of a mole being cancerous - that is very individual. I'll try to say this in a nutshell, but it's a little complicated. A normal mole is called a dermal nevus (dermal=skin, nevus=mole.) When a mole starts to chance or become atypical it's called a dysplastic nevus (dysplastic=abnormal.) There are varying degrees of dysplasia. Mild, Moderate, and Severe. All three of these are NOT cancer. The abnormal cells have a potential to become cancerous at some point in the future though they themselves are not yet cancerous. Once the atypical cells pass the "severe mark" they turn into melanoma in situ which is the most superficial, earliest type of melanoma. It goes on down the line from there with melanoma staging..... way more complicated.
In the practice that I work for I see approximately 350 biopsies a month and two to three come back as melanoma per month. Out of the 150 or so biopsies a month that are ruling out abnormal moles vs melanoma I'd say probably 30-40% come back at least mildly abnormal. That's Florida statistics so if you live up north, you'll probably do a bit better than that.