Need some help from the electronics wizards here.

I know what I need (at least I think I do) but I don't know exactly what I need.

I have a device that outputs 1v AC. When it is switched on, I want it to in turn switch on another device that outputs 12-16v DC.

I believe I need to connect a transistor to the 1v AC output and then said transistor to a relay which is connected to the 12-16v DC output device.

I have a complex and, I believe, rather unique question about DCC.  I am a tinkerer and plan to build my own locomotive turntable.  The turntable will not have a reverse loop controller.  The question I have is if I supply DCC separately to the track that is on the turntable, soldering wire to each side of the track, when the table turns 180 degrees I will have a continuity issue (having created a reverse loop).  However if I have an on/off switch to the rails on the turn table and switch it "off" and have a second on/off  DCC powered switch with the wirin

I built an N-scale structure for my HO layout to place near the top of my mountain to help with forced perspective.  I now realize that I'm spoiled by the "huge" size (in comparison to N-scale) of structures that I've been building in HO!  My hat is off to N-scale (and smaller scale) modelers!

Here's the cabin just sitting in place on my landform before I start doing the landscaping.

I'm going to need to renumber several of the Bachmann Monsanto covered hoppers in HO. I'd like to just change the last number or two of the original reporting marks. Anybody know of a source for matching numbers, and the easiest way to do this?  

thanks! 

Randy