After I changed the fluid I threaded the plug back on by hand, then tightened. I noticed it's not flush with the case after tightening it, however it's tight and no leaks. Normal?

 

Normal

 

Great, thanks.

 

Just did mine last weekend. Normal. I think it is rated for 25 ft-lbs.

 

I do a drain and fill on mine with an aftermarket cover's so that I don't have to remove the whole cover and then reseal to just replace the fluid. I often go into area's where I'm in creeks, lots of mud and water in general so I change it often, as the fluid is cheap and if easy to do you tend to do it more often. I guess that I'm just lazy and now buy my lube by the 5 gal. bucket when it's on sale and do save a little more there also.

Here is a photo of my D30 but many make the covers just make sure the drain is on the very bottom of the cover.