I have a Sound Value Mogul #51810 from around 2012.  I'm going to change the decoder from the Tsunami Sound Value to a LokSound Select.  When I got into the tender today a few questions arise.  There are 8 wires from the single plug coming into the tender.  I can see that two are clearly left and right rail (joined by the tender truck wires), two are apparently headlamp wires (one marked +), two are clearly motor plus and minus.  There are two other tender plug to circuit board connections, each with a black wire from the plug, labeled SMK and U+.  The speaker wires and rear headlamp wires (the + ones marked) are obvious (not connected to the tender plug), the 9th - 12th circuit board connections. 
a) I am not aware that the loco is smoke capable (and not interested if it is).  So can I just ignore the SMK connection and it's tender wire coming from the plug?
b) What is the U+ connection on the circuit board and the plug wire attached to it?  Is it an Aux common positive as on other decoders?  It does not (if I'm doing it right) measure with an ohm meter in common with the headlamp plus and rear lamp + connections.  Is it a separate powered common + that is redundant as the power source for the SMK wire? 
c) I can see the SMD LED for the rear lamp (don't see a resistor there) so I presume the headlamp is LED also? (I'd rather not disassemble the loco.)  If so, for each LED, I presume the needed resistors (for 12v supply) were on the circuit board and I can just (as usual for the LokSound Select 6Aux install ) add a 1k resistor for each LED. 

Any clarification is much appreciated.
Paul