map event trigger

what are commands 73 and 74? where do i find them?

Those two commands are for tile switching. From Imzogelmo's event document (that you should download since you're tackeling events):

Code:

73 : 5    : Replace current map's tiles at A,B with the following D x C chunk, refresh immediately. Upper 2 bits of B determine the layer.
          : Note that the next bytes of size D x C are tile indexes in the tileset of the layer selected.

Code:

74 : 5    : Replace current map's tiles at A,B with the following D x C chunk, wait for command $75 to refresh. Upper 2 bits of B determine the layer.
          : Note that the next bytes of size D x C are tile indexes in the tileset of the layer selected.

Like I stated before you probably will find everything related to the shaking and tiles blocking the path in the entrance event of the map. The offset of this event is clearly stated in LE for each map. If you see 5EB3 as an entrance event, it means there is none, since that event is simple a return.