If you have already submitted a sample, you will get a report. Since 23andme maps your whole genome, they simply compare the existing data as new finding are approved. OR if you are like some and signed up early before the FDA crackdown, you already got all this information and now they are just reappearing little by little.
They don't go that far. A full genome sequencing costs around $2900 as of 2015. (Which is amazing, since the first one cost billions.) Maybe $1000 with the new Illumina HiSeq X Ten sequencing system. Data from a full genome sequencing is about 80GB. (Opportunity here for specialized compression - 98% of the genome for humans is the same.)
23andme is testing for about 100,000 known patterns using a much simpler approach for about a tenth of the price.
Lots of places. Genomics Personalized Health in Santa Monica offers the service to individuals for $2500.[1] Includes cloud storage for the data. They have a list of medical consultants who can help interpret the data; they just give you the bits.
23andMe uses genotyping. IANAMB, but I think that means they run a series of assays each of which "examines" a small PART of the genome to look for something very specific.
As part of their process, however, they could extract the DNA and keep a sample frozen for later assays or even full genome sequencing but I don't know if they do that.
I'm 99.9% sure that a new sample is not required. All of those risk factors can already be looked at with other tools which import raw data from your 23andme account.
Now they sell people only "ancestry" report for half the (now doubled) price. They probably don't get it, but I expect everyone on a "full" plan does. They already have the DNA info.
I got myself tested years ago with 23andMe and you do indeed get ancestry reports. I also get 'pings' every so often from likely distant relatives (3rd-5th cousins if anything).
One lady had been adopted as an infant and was desperately seeking any sort of relative who could tell her something about her origins. I told her what I knew about the families I am descended from but man did I feel bad for her. We were likely distantly related and I'm not sure my info helped, but that would be a pretty remarkable upside to genetic testing for people who want answers.
I was actually able to almost completely solve the mystery of where my great-grandmother came from (adopted as a baby in the South in the early 20th century) using genetic testing.