All the info on NPCs is in the documentation in the file. You'll have to hex edit the data yourself to change which NPCs appear where. For example, the NPC Placement data in Tomra is:
Offset: 9918B
1D 8F 15 BA
01 93 0E 7B
02 84 17 F8
03 8C 05 39
04 9B 17 39
05 9C 16 BA
00
This means that it uses NPCs 1D, 01, 02, 03, 04, and 05 of the Underground/Moon set (take a look at the NPCs document to find out which sprites and speech data these NPCs use). Probably the easiest to do is edit the sprite value and speech data of these NPCs.
Exits (like treasure chests) are also triggers. Take a look at that document. You'll have to change the (x,y) coordinates of the exit triggers to line up with the trigger tiles (the ones with the red dots or arrows).
I've gathered a little more information on the map properties (or map headers), so I'll reiterate it here:
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Location Properties (A9E84-AB203) 13 bytes each
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00: Battle/Spell Properties
bits 0-3: Battle Background
0: Grass 8: Magnes/Sealed Cave
1: Forest 9: Desert
2: Mountain A: Beach
3: Castle B: Land of Monsters/Sylphs
4: Cave C: Tower of Zot
5: Moon D: Lunar Subterrane
6: Ship E: Crystal Room
7: Water F: Underground
bit 4: Warp can be cast
bit 5: Exit can be cast
bit 6: Use alternate palette if available (backgrounds 0, 4, 7, 8, B, C)
bit 7: Battles have magnetic effect if event flag E1 is set
01: Map Index
02: Tileset Index
00: Airship 08: Big Whale
01: Lunar Core 09: Land of Monsters/Sylphs
02: Magnes/Sealed Cave 0A: Tower
03: Castle Exterior 0B: Giant
04: Town 0C: Lunar Subterrane
05: House 0D: Mountain
06: Castle Interior 0E: Cave
07: Crystal Room 0F: Ship
03: NPC Placement Index
04: Border Tile Index
bits 0-6: Border Tile Index
bit 7: ?
05: Map Palette Index
06: NPC Palette Index
bits 0-3: NPC Palette Indices 1 & 2
0000: Palettes 01 & 02
0001: Palettes 03 & 04
etc.
bits 4-7: NPC Palette Indices 3 & 4
same as above
07: Music Index
08: Background Index
09: Background Movement
bit 0: Background is transparent when walking under (such as lakes)
bit 1: Vertical Background Relative Movement
bit 2: Horizontal Background Relative Movement
bit 3: ?
bits 4-5: Direction
00: Up
01: Right
10: Down
11: Left
bit 6-7: Speed (Absolute Movement / Relative Movement)
00: None / None
01: Slow / Moves slowly in character's direction
10: Medium / Moves in character's direction
11: Fast / Moves opposite to character's direction
0A: Map Set From Which to Load
01: Load map from Underground/Moon set
80: Load NPCs from Underground/Moon set
0B: Map Name Index
0C: Treasure Contents Index
I'm working on adding loading the tilesets from the ROM and being able to choose the palette and some other map properties, so you'll be able to do that in the next release.
One thing you should note: if you're loading this map directly from the Overworld, you won't be able to use Tomra's map, since the index for it is in the Underground/Moon set. You could load it from another location map (because the triggers have the ability to do that) but the Overworld triggers don't. Good luck.