The violin and viola bowing techniques would be very similar–the biggest difference would be learning to read the music differently. This isn’t that hard to do, and certainly everything else translates over pretty easily. The other change would be that the viola is longer which would take you having to stretch your fingers a little farther (the 4th finger could be trickier). If you have small hands, I would recommend a 15 or 15.5″ viola to aid in the transition. Violins are all 14″, so that would be only one inch longer if you are used to the size of a violin. The longest viola you can get is a 17.5″ which would be a massive difference from a regular sized violin. Only go that route if you have very big hands.
The viola that I sold Elizabeth was the Vitale viola–it’s a very nice option for the price point. Totally hand crafted and it has a wonderful deep/rich sound.