yes every 2000 or 2500 miles. you need to change the oil more often than a car. in a car it just does the motor. in a bike, it runs through the trans, motor, and clutch and the oil will get dirtier faster.
you should check out
http://www.volusiariders.com/
it is over 6000 members with the suzuki volusia and c50. same bike suzuki just changed the name in 05. tons of info, custom mods, tips, etc.
i have an 04 limited volusia and am a member there.