First oil change - some questions

I have this drain valve on my tank. I connect up a rubber hose to a container, open the valve, no mess. 
https://aircraftsupply.com/product/m12175-oil-drain-valve-12-1-75-mm-rotax-912-914-saf-air-products/

"I have this drain valve on my tank. I connect up a rubber hose to a container, open the valve, no mess." 

Yeah! I have one as well - on my 4X4. I change my car oil about 2-3/year, my aircraft 1/year.

My car, pre valve install, required removal of a steel plate and even then then was always a messy job, draining 10L of hot oil,  in cramped confines.

My aircraft, 3L of oil, easy to access, no mess.

😈

Thanks all for your replies and advice!

I did the oil change, everything went well. Zero spill when draining the tank, the valve is just over some bars of the engine mount, so I used a milk box cut in half (inspired by Kevin's idea) as a home-made funnel which poured all the old oil into a 10L container (see the photo).

Removing the filter and the magnetic plug was a little bit more problematic. I could not find a way to avoid the spillage completely and I had to clean some parts of the engine afterwards. But I got some ides to to it better next time.

I refilled the oil, checked the level, cranked the engine by hand 20 rotations as per MML, and there we go. One thing I noticed is oil level took a little bit more of time than usual to rise: on my engine, usually it is almost instantaneous after start, but on first start after oil change it took something like 1 second. Still within specs, but I can tell you it was a looooong second with my eyes fixed on the oil pressure gauge.

Warmed up, re-checked oil, went for a short flight, all fine:)

Afer the oil change I did, and just trying to learn more about how the lubrication system works, I have been reading the manual and SI about the purging procedure.

I know normal oil changes do not require a purge. However, I realize I did something I would not do the same next time: after draining the tank and changing the filter, was so late, I decided to inspect the plug next day. And I did NOT refill the tank until I had inspected it, meaning the tank was empty for some 12h.

The engine was not cranked with the empty tank as MML clearly advises against it. But I did not see any note about refilling quickly. Now, given oil pressure was obtained quickly on start after the change, and engine runs fine, I think everything is right, but the documented valve tappet problem worries me. My understanding is by design, the cooler being lowest point, as long as you do not crank the engine causing oil to move through the circuit potentially "sucking" air from the empty tank, you are ok, and that is the reason a purge is not required. But I have seen a couple of posts (that I did not see before!) about not letting it sit overnight with the tank empty as residual leaking could cause air in the system.

So my question is: does a oil change procedure, no drain galleries, but an empty tank overnight, require an oil purge + tappet inspection?

Thoughts?

Personally I wouldn’t leave the tank empty for any longer than necessary for the reasons you’ve stated. 

However if you have good oil pressure and no tapping noises with the engine running then you don’t need to worry about purging the tappets.

You are only likely to have a problem if you have either drawn air into the system by rotating the prop with an empty tank or breaking into the oil circuit somewhere such as removing a hose.