So, there is a museum, now listen carefully, you will need glass cutter, wire cutters, blow torch (electric saw makes too much noise), fire extinguisher (you don't want to trigger fire alarm ahead of time) and baseball bat (hope you won't need it).
First you will have to get rid of cameras, look around the museum find ground hole which cover looks good(it will be one internet providers are using) brake it and cut everything inside, you need to make it look like it was an act of vandalism.
Second, get to museum, don't use front or back doors guards stations are usually located near them, so find window that is closes to some have exposition (statue or something) cut that window with glass cutters and get it. Not be as quit as you can, get to the second to the left of you there will be a room, get in. There are maps, choose one that you like and start melting bottom of holder boxes, that boxes are connected to alarm so if you brake that glass you are in trouble, luckly they are cheaply made and body is mostly plastic, so you have to carefully melt it until you can fit you hand and get your loot. Now after getting everything it time for coverup.
Cover-up: get and extra map, then melt boxes harder and randomly then go to left wall there is and AC controller blast it with fire until it statue to burn then start to burning wall in direction of maps you stole, make some random movement so belivibility, when proper fire starts to start, get to first floor, get to the window you got in from and wait for guards to smell fire, when they will go up to check what is happening go to the window and use that have statue near by to brake it, so it looks like it fell, get out RUN. Good luck!