Even though plumbing is one of my less favorite DIY tasks, ...I installed it myself.
The removal of the old water heater was more difficult than installing this new one. Installation time, : apx. 45 minutes after the old one was removed, and "POOF"... had hot water
If you're looking for minimal installation headaches, and costs, try to get something as close to the same height as the old heater. In doing this, I spent about 4 bucks on copper pipe, and 2 copper couplings. (see photos) This made up the small difference in the installed height between the two heaters. (Please excuse the amateur copper soldering job!)
I lucked out when it came to attaching the gas line - exact fit without any further parts.
Hope this helps,