The setting for Ukrainian Job should look familiar: you're back at the Precious Things store from the Jewelry Store job. This time around, you need to steal a tiara.
This can be done as another smash-and-grab job á la Jewelry Store, but only if the tiara spawns in a jewelry case in the main room. See, this time around the store has metal detectors, so you'll be made the second you enter that room.
A good approach to take is to enter through a window to either side of the store, but don't forget about the patrolling security guard! Make sure he's neutralized before you start breaking and entering. You'll need to wear the mask to do any of that, so you'll be ready for action once you're in the store proper.
Check the safes in the rear rooms for the tiara before entering the main room. If it's in either one, grab it and leave the way you came. If not, you'll find it in a case or on a shelf in the main room. In that case, rush in - this will trigger the alarms - and find it as soon as possible. If you can snatch it up before your getaway driver gets spooked, you can reach the van in good time.
Should the job turn into a shootout, you can hold out in either the rear rooms until police forces ease up. Both rooms provide some cover, but you'll have to watch both the doorway and the windows.