It sounds like your Dad took careful care of his magazines which should help the value somewhat but frankly Karen, with a few exceptions there does not seem to be a thriving market for older issues of Trains magazines. At the train shows I go to some people try to sell them for $1 a copy, with some takers, but I have also been at train shows where each issue sells for twenty five cents and even then they sit unsold.
Others bundle them up by year and sell a year for $5 or so.
The exception is issues from the early 1940s (when it was physically much smaller) and the 1950s, but even then, that is where collectors are often looking for just one or two issues to fill out their complete set. I have seen those sell for $2 an issue. Extremely desirable issues might go for more. One example: here in Milwaukee the April 1948 issue which had a major feature and map on Milwaukee can go for $3 and more an issue. Other particular issues have taken on their own almost cult like status.
Most collectors like completeness -- by year or by volume (which did not match calendar year with Trains back in its earlier years). That means they seak out this or that month from this or that year but are unlikely to be in the market for a big collection of Trains.
I suggest separating them by year and trying to sell them by year; and at least initially resist breaking up a year. If the price is reasonable someone will buy a whole year to get an issue or two they really really want. But a big box of Trains sold as a unit is likely to involve so much duplication for most of us that there might be few takers.
I hope this helps.
Dave Nelson