I have tried reading the documentation about plugins and making small edits to the script to resolve those errors, but I just cannot seem to get it to work. Can anyone help me edit this plugin in a way that makes it work with GIMP 3.2?

Another request is to add to the script to also add guides around the perimeter of the canvas. Which I assume should be simple, just adding something like

(gimp-image-add-vguide img 0)  
(gimp-image-add-vguide img 100)  
(gimp-image-add-hguide img 0)  
(gimp-image-add-hguide img 100)  

::: spoiler Original plugin script

;===============================================================  
;== GIMP Add Guides Vertically and Horizontally @ 50%         ==  
;== Copyright (c) 2008 Gregory M. Ross                        ==  
;===============================================================  

(define (script-fu-crosshairs img drawable)  
  
    (let* ((ImageW (car (gimp-drawable-width drawable))) 
	    (ImageH (car (gimp-drawable-height drawable))) 
	    (Vert_Offset  (car (gimp-drawable-offsets drawable)))  
	    (Horz_Offset  (cadr (gimp-drawable-offsets drawable)))  

	 
	    (Vert_50  (+ (* ImageW 0.5)Vert_Offset))  
	    (Horz_50  (+ (* ImageH 0.5)Horz_Offset))  
    )  
   
    (gimp-image-undo-group-start img)  
    (gimp-image-add-vguide img Vert_50)  
    (gimp-image-add-hguide img Horz_50)  
    (gimp-image-undo-group-end img)  
    (gimp-displays-flush)))  


(script-fu-register "script-fu-crosshairs"  
		    "<Image>/Image/Guides/Crosshair Guides"  
		    "Add Guides at 50% Horizontal and Vertical"  
		    "Gregory M. Ross"  
		    "Gregory M. Ross"  
		    "March 2008"  
		    ""  
		    SF-IMAGE    "Image" 0  
		    SF-DRAWABLE "Drawable" 0)  
		    

:::