I'm in that business, and (from the sounds of it) what you got is actually BETTER than the thicker stuff--IF you prepare and apply it right.
The thicker vinyl is the cheap stuff that's rolled out like bread dough when it's made, and then backed with a cheap adhesive.
They do not recommend this for car applications for two reasons.
First, the adhesive has a two year life when exposed to outdoor conditions; and second, as it sits on whatever it was applied to, it will try to shrink over time back to it's "original" shape, which will cause it to leave an ring of adhesive around the decal where the vinyl shrunk, but the adhesive didn't.
The thinner stuff (like you got) is melted and then poured out and allowed to cool, which makes it alot more dimensionally stable but thinner.
It has an outdoor lifespan of 7-10 years, depending on which specific vinyl they used.
The adhesive on the thinner vinyl is alot better, and the thinner material is less likely to edge peel on you, as well.
The "protective masking tape" you got is actually application tape, which makes it alot easier to apply the graphics without bubbles, etc...
Here is a site (not mine) that has instructions for properly applying the decals like you got.
http://www.speedysigns.com/info/application_instructions_large.asp They didn't recommend making sure your surface was SMOOTH before making sure it was CLEAN because they assumed you were going to put the decals on your car in the pictures; but that something you need to keep in mind before putting ANY decal on.
Even the thicker vinyl will show imperfections in the surface below it.
As far as the cutting goes, that is really something you don't want to do until AFTER the decal is down.
You use the squeegee to push the vinyl into the corners, and then trim after it's there.
That way the decal fits perfectly, and wall to wall.
I'm sure you'd have been even more upset if they had trimmed the decal to the "standard" size, and you found out your cabinet was 1/2" wider, wouldn't you?
The small imperfections showing through the vinyl usually aren't that big a deal.
The thinner vinyl gives it a "painted" type look.
If you've got some BIG imperfections, you need to fix those before you apply the vinyl.