Look at it this way, what have you done wrong? You shopped (I assume you have proof of purchase) and their machine malfunctioned?
It's up to them to prove you parked and are liable to pay.
But why not appeal stating the facts and providing proof of purchase...even if it is past the deadline.
80 is what I'd use to remove the paint to bare metal, then if painting on bare metal I'd finish at 240 before priming/undercoating. If painting on existing paint I'd be at something like 600 grade before undercoating.
It really does depend on what you want, for most flexibility, design in software of your choice and export as PDF. If you're after a printed vinyl then I've used Stickers International a few times with no complaints - they even have a basic online design web site.
This is quite a simple task and the Autoidesk tutorials are good but it's no good just jumping in - you need to run through them in sequence, your Autodesk login keeps track of what you have and haven't completed.
For most modelling tasks I take a little time to think how I'm going to model it...
I think 80W/90 is equivalent to ISO100 so going for an ISO 100 non EP gear oil may be your best bet. A hydraulic oil might be your best bet.
Edit: might be worth asking Westway Lubricants - https://www.westwayoils.co.uk/
A word of caution, if you drill bang on centre and straight, the stud will remain until the very end. At which point the remains of the thread will be drawn up the drill flutes wrecking the hole on the way....if you're lucky it will be ok for helicoil, of not you need something else...e.g the Ezelok
So it was working fine until you decided to service it? If that's the case I'd be looking at something you've disturbed....got the contact tip back correctly, disturbed something on the ground terminal.....?