The fire damage to #7 was mostly limited to the fireman's side of the cab and the water tank.
The tank is a complete loss, as the already thinned sheet metal was burned clean through in several areas. The insurance on the locomotive will cover the price of a completely new tank, and the last that I heard was that MNG was bidding out the construction of said tank.
The upper framework of the cab will probably need to be replaced, but the flooring looks like it is salvageable.
The locomotive frame, trucks, running gear, castings, and anything else I forgot to mention that was at cab floor level or below appeared to have escaped even minor damage.
Luckily, the vast majority of #7's critical parts (boiler, accessories, piping, cab roof, etc) were either off site or stored in a different location when the fire occured. In fact, having swapped #7 into the location where we would normally have #4 stored saved that locomotive from any possibly disasterous damage. As it is, #7 was already taken apart, and will need far less work to get back on schedule than would have been needed otherwise.
Speaking of #4, she has been laid up since late November 2009 with staybolt issues. What can be done to make her operational again is currently being investigated, so stay tuned for updates on that.
What can be said is that there is probably not going to be steam on the MNG this year. However, that doesn't mean that things can change in the near future.