Easy enough to do normal periodic service, assuming decent access: oil and filter changes, impeller changes, fuel filter
filter changes. Yes, add the oil exchange pump, although I'd be surprised if the Riviera didn't already include that.
Not too much more difficult to do your own aftercooler service, AirSep service, belt replacement. Valves only slightly more intricate, mostly since you'll need gauges.
-- emptying, purging, refilling -- is slightly more difficult, but that's more about capturing and recycling quantities like that.
DO order the service manual.