Long post, several answers in one go:
MicroDem versions: It doesn't matter which currently available version you get, it won't be the same as the tute. Lat time I installed on a new computer I looked hard for a source of the tute version simply because I was accustomed to using it. I couldn't find a source.
GIS and Seamless: If you persist with the GIS data what you are downloading is 'Quads'. Quads cover a pretty small area, so to make a decent sized proto route you will need to combine several quads. I like big routes and some of mine have 50+ and IIRC one nudges up towards 100. 'Seamless' data on the other hand only needs one (large) download. I like Quads (cause I'm old, doddery, and stuck in the past) the younger set prefer seamless. In the end product it makes little difference.
Merging Dems: 'merging', which you will need if you persist with Quads.. About half way along the top M'Dem toolbar is a button with two horizontal arrows labelled 'In - Out'.
'In - Out' > Merge > DEMS > Pick Single > then just click successively on each Quad to be merged. I find the alternate 'Pick Multiple' option unreliable.
10m and 30m: When the tute was written it was all 30m data, so the option wasn't an issue. Now lots of 10m data is available. If your route has all one or the other use it. Often though some Quads will only be available as one or the other. 10m DEM is more accurate, but you are making a simulated train route on a computer, not planning national defense strategies. 30m DEM is plenty good enough for Trainz, the data packs are smaller and you can merge much bigger maps in M'Dem using 30m than you can 10m. So I opt for 30m wherever it is still available.
If you are stuck with both though, merge all the 30m and save. Merge all the 10m and save. It does not matter if the quads are not adjoining. Now open each merge in succession and from the top toolbar File > Save DEM > DTED > accept defaults and save. Do the same for the other merge. Now merge the DTEDs. Save that merge with no options and you will revert to the format used by HOG.
With a big route you will get to the point where M'Dem can't cope with the merge. You will get there quicker with 10m Data. At that point you need to start making multiple routes and merging in Trainz. We'll cover
that when you get there
I need coffee...
Andy
