It won't come out as good, but yes it is possible. The most important thing about sushi rice is that it is very sticky. This is best accomplished through buying the proper variety of rice (if possible) and cooking technique.
To make the rice sticky: 1) do NOT rinse the rice before cooking-- this ensures that the starch remains in the rice. 2) Prepare the rice as you usually would, but stir it several times while it cooks. This will make the rice sticky. 3) Make sure you add enough water (about 2x water-rice ratio). If there's not enough water, the rice will be hard. 4) If possible, use short or medium-grain rice. Long-grain rice still works (I've done it), but it won't be as sticky. 5) Season the cooked rice with rice vinegar to give it the proper flavor.
Yes you can, just make it a little wet than usual, but the most important thing that you do is to add rice wine vinegar as soon as the rice is cooked and still hot.
it won't be great, but it will be good enough.