Here is what I've done so far.
1. Replace the old wall switch with the 2476S switch
2. Plugged the 2412S modem into the wall and connected the serial cable into the Core.
3. Open the Admin page
4. Wizard > Devices > Generic Serial Device
5. Add Device
6. Pick device template 1932 (Insteon PLM)

7. Software begins to download, then the "finished" message appears telling me to restart router.

8. Go back to admin page, select device, and see errors

9. Go into advanced tab and select controlled via Core, serial port ttyS0, save, restart router.
10. No workee. "Send command to device" reports fail. GSD log does not exist in Pluto folder.
11. Reboot computer and see more software download (rubytlk or some such). Now I can send commands to the device, the GSD log exists, and the LED on the modem begins to flash. But I still can't control the light. Below, for your viewing pleasure, is the tail end of the log (after the 2600 lines of start code).
2601:end
2603:(***):MY DEVICE:38
(***):SndIns:Queue:[36m1[37m
(***):[32mout:02 6B 40 Length:3[37m
(***):X-----------SndIns: Waiting for response to:SetCfg
(***):X-----------SndIns: Current Queue Length:2
(***):Finding Children..
(***):reading stored Child configuration:
(***):********************************************************
(***):X-----------SndIns: Waiting for response to:SetCfg
(***):X-----------SndIns: Current Queue Length:2
(***):[31mIN:02 6B 40 06 Length:4[37m
(***):SetCfg Completed
(***):[32mCommand Completed.[37m
(***):SndIns:Queue:[36m1[37m
(***):[32mout:02 69 Length:2[37m
(***):[31mIN:02 69 06 02 57 E2 01 0A 97 0B 01 01 FF Length:13[37m
(***):GetLnk ACKED
(***):LnkData Message Received
(***):{"Parameter2"=>"57", "Parameter3"=>"E2", "Parameter4"=>"01", "Parameter5"=>"0A", "Parameter6"=>"97", "Parameter7"=>"0B", "Response"=>"LnkData", "Parameter8"=>"01", "Parameter9"=>"01", "Parameter10"=>"FF", "Parameter1"=>"02"}
(***):record Flags:E2
(***):Controller
(***):Insteon ID:0A.97.0B, Group:01
(***):[32mCommand Completed.[37m
(***):SndIns:Queue:[36m1[37m
(***):[32mout:02 6A Length:2[37m
(***):[31mIN:02 6A 15 Length:3[37m
(***):sendGetNext NACKED
(***):[32mCommand Completed.[37m
(***):Entered CheckChildRecordsinPLM
(***):Record: = 0A.97.0B Group:01
(***):checking to see if it needs to be added as a child...
(***):ExistsinChild:InsteonID:0A.97.0B
(***):ExistsinChild result:FALSE
(***):0A.97.0B needs to be added to the child database
(***):addtochild Routne called
(***):Adding 0A.97.0B to the child database...
(***):Child is Insteon
(***):PING Sent!
(***):0A.97.0B exists in PLM
(***):SndIns:Queue:[36m1[37m
(***):[32mout:02 62 0A 97 0B 0F 10 00 Length:8[37m
(***):[31mIN:02 62 0A 97 0B 0F 10 00 06 Length:9[37m
(***):Got PING ACK
(***):[31mreceive timeout=1[37m
(***):[31mreceive timeout=2[37m
(***):[31mreceive timeout=3[37m
(***):Command Stalled! resetting and retrying
(***):Current Command:1
(***):SndIns:Queue:[36m1[37m
(***):[32mout:02 62 0A 97 0B 0F 10 00 Length:8[37m
(***):[31mIN:02 62 0A 97 0B 0F 10 00 06 Length:9[37m
(***):Got PING ACK
(***):[31mreceive timeout=1[37m
(***):[31mreceive timeout=2[37m
(***):[31mreceive timeout=3[37m
(***):Command Stalled! resetting and retrying
(***):Current Command:1
(***):SndIns:Queue:[36m1[37m
(***):[32mout:02 62 0A 97 0B 0F 10 00 Length:8[37m
(***):[31mIN:02 62 0A 97 0B 0F 10 00 06 Length:9[37m
(***):Got PING ACK
(***):[31mreceive timeout=1[37m
(***):[31mreceive timeout=2[37m
(***):[31mreceive timeout=3[37m
(***):Third attempt, Failing Command!
(***):[32mCommand Completed.[37m
(***):[33mQueue Empty.[37m
(***):RERUN=TRUE, RESTARTING
(***):SndIns:Queue:[36m1[37m
(***):[32mout:02 62 0A 97 0B 0F 19 00 Length:8[37m
(***):X-----------SndIns: Waiting for response to:SndIns
(***):X-----------SndIns: Current Queue Length:1
(***):[31mIN:02 62 0A 97 0B 0F 19 00 06 Length:9[37m
(***):[31mreceive timeout=1[37m
(***):[31mreceive timeout=2[37m
(***):[31mreceive timeout=3[37m
(***):Command Stalled! resetting and retrying
(***):Current Command:25
(***):SndIns:Queue:[36m1[37m
(***):[32mout:02 62 0A 97 0B 0F 19 00 Length:8[37m
(***):[31mIN:02 62 0A 97 0B 0F 19 00 06 Length:9[37m
(***):[31mreceive timeout=1[37m
(***):[31mreceive timeout=2[37m
(***):[31mreceive timeout=3[37m
(***):Command Stalled! resetting and retrying
(***):Current Command:25
(***):SndIns:Queue:[36m1[37m
(***):[32mout:02 62 0A 97 0B 0F 19 00 Length:8[37m
(***):[31mIN:02 62 0A 97 0B 0F 19 00 06 Length:9[37m
(***):[31mreceive timeout=1[37m
(***):[31mreceive timeout=2[37m
(***):[31mreceive timeout=3[37m
(***):Third attempt, Failing Command!
(***):[32mCommand Completed.[37m
(***):[33mQueue Empty.[37m
(***):RERUN Not needed
(***):Reporting Child Devices
(***):Child:0A.97.0B
(***):Config:["****************"]
(***):0A.97.0B
This seems like progress to me, but I don't know what comes next. I think I have to push and hold the modem reset for 10 seconds, then go do the same on the light switch. The LEDs blinked but not much else happened. How do I tell LMCE that there is a light to control?