You can certainly do it yourself if your up to the challenge. The challenge being, breaking the hex nut loose without damaging anything.

The job is much easier with a breaker bar.

Good luck!

There is more here about anodes than you might want to know. One complicating factor is adequate overhead space to remove the old anode and install a new one. It is not that difficult to deal with though.

http://www.waterheaterrescue.com/pages/WHRpages/English/Longevity/water-heater-basics.html

"One complicating factor is adequate overhead space to remove the old anode and install a new one."

Replacement anodes can be obtained that are segmented.

Removing the old one may require cutting it up.

Use a 3/4 in drive socket set and a breaker bar.

Hit up a rental place, they are expensive.

Do not drain the tank before trying to break the anode screw loose, but turn off the supply to the tank.

The weight is to your advantage in keeping the tank form moving.

As soon as the fastener starts to rotate THEN stop and drain the tank (making sure the power source, gas or electric, is OFF).

Electric or air impact with 6 point IMPACT RATED socket judiciously applied while wearing safety glasses is the easiest way.

You can buy a nifty 1/2" drive electric impact at Harbor freight for around $50. Once you're done with the anode you
ll find lots of other uses for the impact.