This is similar to the code I used in my game "Quarantined"
You'll have to change the Hud_image.dds to the name of your file and change the position of the Hud to your liking, but it'll display your hud for six seconds when the F1 key is pressed.
;Artificial Intelligence Script
;BY: NUE B.
;Header
desc = Display Objectives (push "f1")
;Triggers
:state=0:hudreset,hudx=50,hudy=90,hudimagefine=gamecorehudsHUD_IMAGE.dds,hudname=OBJ,hudhide=1,hudmake=display,state=10
:state=10,scancodekeypressed=59:hudshow=OBJ,state=1
:state=1:timerstart,state=2
:state=2,timergreater=6000:state=3
:state=3:hudunshow=OBJ,state=0
;End of Script
*** The Object you attach this code to must be dynamic and must be set to Always active!!! you may want to make it immobile too.