With some mechanical skill, it is straightforward job. Some basic hand tools (metric) and the shop manual will take you far, even lacking experience. Removal of the air cleaner is necessary, but take your time and follow the procedures and you'll do just fine.
Doing your own service work will NOT void the warranty. However, let's say you change the oil in the mower, but don't put enough back when refilling, and the engine seizes up from a lack of oil. Such damage is not a factory defect, and repairs to the engine would not be covered under warranty. Further, let's say you did the oil fill wrong, and a wheel adjuster breaks. There's no likely reason the adjuster broke because of the incorrect oil fill, so Honda would probably pay under warranty to repair the adjuster.
Some Honda dealers do provide on-location service, but for a fee. Contact and discuss with your local dealer for details.