The motors themselves determine what amp decoder to buy. If your loco's are new HO they probably don't pull more then 300 to 450 milliamps when running.
However, you should purchase decoders based on the stalled amp rating of the motor.
You would need an amp meter to determine this and do the...
It is pretty simple to have the programming track as part of your layout.
I simply use toggle switches to make a small section of my layout my programming track.
I therefore can run my loco from the programming track area, after programming, to the rest of my layout without having to pick up...
I would be hesitant to install a N or Z scale decoder into an older Athern loco. They draw a lot more current then newer model.
While they may fit, the current may be too great and at least shut down the decoder due to overload.
Wire the RED and BLACK wires to your PROGRAMMING TRACK.
Then read the CV's to get the manufactures ID.
The wire colors seem to match current decoders.
CV 8 contains the ID. The link below should help.
http://www.tonystrains.com/technews/dec_rescue.htm
I find Model Railroad News to be an excellent read. the articles are more comprehensive then most of the other magazines.
I subscribe to Model Railroad, Craftsman, Model Railroader as well.
That is a great source for # 14 or #12 stranded bus wire. They have 100 foot extension cords that contain #12 or #14 wire and by striping off the orange cover you get really nice heavy bus wire. Plus the ground wire works fine for feeders to the track.
Yep, they have an extensive stock and are real friendly.
I visit Tucson once a year and save up my pennies just to shop at the ACE store!
I have purchased a couple thousand dollars worth there in the past 3 years.
The train department keeps getting larger each year.
I have traveled all over...
I use DecoderPro with my Lenz DCC... sure does simplify all decoder programming.
Very easy to use and the price is right! FREE.
Here is a link to DecoderPro.
http://jmri.sourceforge.net/apps/DecoderPro/index.html
I have built large Walthers buildings as well as CPM and have used the Model Craft (Testors) in the black bottle. It has a very thin long tube that really works well.
One bottle will build almost a complete layout's worth of buildings.