@ Blackshadow...I think your Corso's crop is beautiful, but you can't really do such a short crop on a GM/GD. With GD's you really have to post and tape.
@ DD
My GDs were all cropped by the breeders, so I don't have any really good suggestions for locating a good vet, other then looking at pictures of Danes whose crops you admire; then locating someone who does ears and asking if s/he can do the crop. The Doberman vet may be a good resource if s/hes done Dane Ears as well -- as Dobermans have three different lengths of crops as well (working, medium and long show). You could try asking some Dane showing breeders (who tend to be very particular about their crops) in your area for a vet reference. They may be a bit reluctant, since you are not buying the puppy from them, but it's worth a try.
I've personally always preferred a longer show crop, but it depends a lot on what length will best complement your pup's head (which is probably why the Dobe vet wouldn't offer more info/advice until she saw your pup). A disadvantage of the longer crop is that it usually takes a lot longer to stand.The best age to do a Dane's crop is between 7 and 10 weeks; but I have known people who had success with pups up to 14 weeks.
In terms of prep, find out which method of taping the vet will use (the most common for Danes are with pipe foam, ear inserts (Dr. Scholls soles cut to size) and tongue depressor bracing, or taping to a styrofoam cup placed upside down between the ears. There are several other approaches, as well. So when you know the vet's preferred method, get lots of supplies. In terms of the pup, preparing him/her will be as with any surgical procedure -- no food or water within a specified time frame before the cropping. We also used hydrogen peroxide for cleaning and bacitracin for the ear edges. Your vet will give you lots of instructions on ear care and re-taping. Generally stitches can out within 8 days. Until this happens (and sometimes up to a month after) the vet may use foam posts or methods that don't irritated the cut edges. When the final taping is done, you only have to re-tape the ears about once a week, unless there is a sign of problems (bad odor, shaking the head).
With the long crops I had done with my GDs, it took between 14 and 18 months for the ears to stand (and stay up). It does take commitment, but I never found it too onerous or difficult and I loved the outcome!