FRED2 crashes because it's still missing some files. You need to copy the game palette pcx files to data\effects for it to not crash. Also, FRED2 (the original version) seems to have trouble setting the nebula 1 settings when you load a file, though it can save them. (We could use an "Ok" button on that editor, clicking the close box does not save changes you've made at least in the original version.) The last thing I think you need (I'm not entirely sure what I got was a FS1 nebula, but it was really odd, will describe it later in this post.) to do is change the mission flags. From looking at the source code, it seems to check for the full nebula flag, but if the full nebula flag is enabled it won't save nebula 1 info. So, save your mission, turn on the full nebula flag, and save another copy of the mission. (Don't change anything else.) Then copy the flag entry from the mission you just saved to the one you saved before via a text editor and save it. (My simple mission had flags: 0 and the full neb version had flags: 4. I copied the 4 over.) You should now be able to play an FS1 nebula mission. (I'm not sure if the original exe will play them, mine is crashing when I try to run it, but I wouldn't think a mission would crash it before it gets to the login screen, will retry after I reboot. Some other programs crashed which might be affecting it.)
And now a description of what I did get:
I used Nebula03 and Grey Green in the background editor. I was flying around in a really odd looking nebula that changed colors when I changed direction. I could not target any other ships (maybe awacs info and/or an awacs ship is needed?) and the nebula did not look like any I remember seeing in FS2. (I don't remember playing any FS1 nebula missions.)
Addendum: Set the range thing for the fullneb version and copy over the +NebAwacs: entry that's right below the flags entry in order to set the radar range.
(PS Interesting note, I think the variable that counts the total messages in the mission for the comment is used uninitialized, it says I've got 207 messages total when I really have none.
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