Looks like your brother did good! Check out the fuel lines, if they haven't been changed over recently thay may not like the new gas.
Make sure you have carbon monoxide and fire detectors and fire extinguishers. If missing or old replace them.
I could probably go on for pages, but this will help prevent fires and keep you breathing.
The carbon monoxide detector will work not only for your rig, but the one close by with the generator running.