I used Reveal for the very first time myself recently, so I think I know what you'll want to know
Here's my overview...
a) The DF Wiki is well-maintained, and a huge help not only for gameplay questions:
http://www.dwarffortresswiki.net/index.php/Utilities#Revealb) The DF File Depot is also great, but I usually search for stuff on the Wiki and then look for wimbli URLs
This is the version I use (because I didn't have to install any additional drivers to use it):
"Old version of reveal (a tool that reveals tiles of a map in fortress mode), with updated memory.ini file for version 0.28.181.40d"
http://dffd.wimbli.com/file.php?id=645c)
Your DF data folder contains: data folders, and a save folder.
The data folders apparently stay the same no matter what you do - all they do is provide info to the game. Whatever you do is stored only in the save folder.
So it shouldn't be necessary to backup anything ... except dwarffort\data\save
d)
My own repro steps:
0. Extract
http://dffd.wimbli.com/file.php?id=645 so all the files including reveal.exe are in your dwarffort folder.
1. Start DF. Keep playing with Location Finder and new worlds until I find an embark which I like.
2. Immediately after arriving, save the game.
3. backup the save folder (= copy the folder dwarffort\data\save to dwarffort\savescum\00start\save)
4. Start the game and continue.
5. Zoom to the bottom level, and assign all of it to be mined.
6. Remove Designation on the bottom level.
7. Doubleclick reveal.exe
You'll now get a little text window for like a split second.
Afterwards, all of the map should be revealed.
If you continue playing on the revealed map, you'll see serious bugs, so, erm, don't:
8. Scroll around the map, possibly noting highlights on a piece of paper.
9. Save the game
10. Make a backup of the revealed fort if you want (= move the folder dwarffort\data\save to dwarffort\savescum\00xstartRevealed\save)
11. make sure that dwarffort\data\save no longer exists
12. Restore the backup (from before you used reveal): copy the un-revealed save back into DF: copy dwarffort\savescum\00start\save folder dwarffort\data\save
e) Have fun
f) I did all of the above for my last fort, but then discovered that a) I haven't brought food on embark and b) I brought two cats. Did one false start which lasted a game year (during which the fort became increasingly filled with a miasmic purple haze ... first time I brought cats. Mistake.) This time I managed to build two cages and trap both cats before the damn creatures could adopt a dwarf. Now ... what's a fire snake?