Zanussi Assembling Error - Please help !

I have a Brand new Zanussi 300 / ZWF91283W. I am also complete novice at washing machines.

Prior to installing at the rear of the machine I am required to remove 3 holding bolts. Thereafter there are 3 plastic stoppers (2 large at bottom,1 small at top) I am required to fit to fill the holes.(see photo).

I found the small top plastic stopper very fiddly and like an idiot I managed dropped the small plastic stopper into the hole at the back of the machine.

I phoned Zunussi. They said that as a foreign object had fallen into the back of the machine then this could have a negative impact on the machines performance. Also the machine would not work without the small plastic stopper fitted at the top.They said they wouyld need to send an engineer out to remove the plastic part - of course at my expense. This appears massively galling, paying out £100+ prior to even plugging the machine in. Just for the sake of a tiny plastic part the size of and costing less than one pence ?!?!

In fairness to Zanussi they are sending me this small plastic part free of charge.

I have 3 questions if I may ?

1) Having fallen into the back of the machine, is the small plastic stopper really likely to cause damage to the machine ?

2) If answer to 1 is yes, whilst a total novice, might I be able to remove the 6 small bolts at the back of the machine and take out the small plastic stopper ? Or would I need to call in a repairer ?

3) If answer to 1 is no, would I need to await for the arrival of the replacement small stopper before using the machine ?

This is so frustrating - any advice would be hugely appreciated ;-0