I wouldn't use Locktite on the adapter, but Teflon tape or paste to seal it. Also, keep the tape away from the last frew threads, as you don't want any remnants from coming loose and getting into the oil lines. It is a pipe-thread fitting and goes in tight and secure without Locktite.

Teflon tape. I didn't drain the oil, but just did the swap quickly, losing only a few drops of oil.

I raised the tank and inserted only the sending-unit wire in some plastic tubing, then pushed it through to the right front side of the tank to flow into the fairing with other wires in that location. You can run the wire under other wires at that point (top-front frame juncture) so that it doesn't add to the clutter. Ground the sender to anything close by, like one of the two ground connections in the recessed area under the seat and in front of the battery. There's no point running a second ground wire from the sender all the way to the gauge. You will, of course, need to ground the gauge somewhere inside the fairing using a separate wire. I used the wires from the old air-temp gauge for ground and lighting. You can tell which to use by their location on the old gauge.

FWIW, the adapter you'll need is a 1/8" female to 3/8" male. Neither AutoZone nor Home Depot had this fitting locally, but Napa did.

HD taps off the return line from the engine, which is probably the best location to read temperature being the hottest environment, but it's a much more complex install. On my '07 you needed an oil-filter adapter ($50), but if you already have the newest oil cooler (26155-07) this adapter will already be in the kit. You can then tap into the return line at that point, which is outlined in the gauge instructions.

However, every auto and MC I've owned since 1982 has had an oil temp guage, always installed by me, and the temperature source was always the oil pan, so I'm atuned to readings from that location. You can figure that oil in the engine will be 10-20 deg. hotter than in the pan.

Not in my opinion. The pipe threads go in tighter as the adapter and sender go in, and should never be a problem. As I said before, I used Teflon tape.