Years ago I used a rattle-can upholstery spray on an old beater V-dub beetle. I did the door cards and vinyl seats and went from red to black. I was amazed at how well it held up. Sold the car 3 or 4 years later and it still looked good—seats and doors. 

Re: Carpet. I'd recommend you purchase pre-molded carpet from our host or the manufacturer (i.e. Newton). I suspect by the time an upholstery shop cut, formed and fitted generic carpet from bulk stock, the cost would surpass top-end pre-cut molded carpet. You can always purchase molded carpet and have a shop simply apply adhesive and install if you're not up to the task yourself.

It would depend on the plaid....

Door cards being flat, is shouldn't be too hard to DIY recover them. If using a woven fabric, it could be applied using a spray-glue. The tricky parts would be the rounded corners that may tend to be warped outward with age. If you want a softer feel, you could get a fibrous polyester padding like thin quilt batting. The same could be done with upholstery-grade vinyl, though the glue you use must be compatible.

I'm not sure if the lower portion in vinyl would work that well - the seam between fabric and vinyl would have to be sewn and the dissimilar materials may bag and sag.

To solve Willie_B's shoe-kick problem (we all have it), maybe you could source a guard panel out of heavy-duty plastic, metal or carpet. The MK1 cars have a great solution at the front of their (real) door pockets.

Take it to the upholstery shop and ask the same questions? they deal with this stuff all day and would be able to give you cost at the same time as well as matching the colours to your existing seats.

That's a good idea!  it would still give the bit of flash I'd like, but be practical, too.

Any ideas about the carpeting?

I find myself hitting the door card with my shoe when getting out of the car. By looking at it I do this more than I think. So not sure how cloth would hold up. Maybe cloth for the upper 2/3rds and vinyl on the lower.

Never considered that.  Do they come in white, and can they be dyed?

What about dying door cards to match colour that you want

This might be a stupid question, but I'm gonna solicit opinions anyway.  The burgundy-color door cards on my classic are worn and really need to be replaced.  I know I can buy replacements, but they probably wouldn't match very well, unless I changed to plain black.  The alternative would be to find an upholstery shop to make them with a heavy fabric, perhaps a plaid.  Would the value of my car plummet to zero with such a non-standard card?  (I'm kidding.)  Or would there be other considerations that would make it a bad idea?

Along with that, I'd like to replace the worn red carpeting.  Perhaps the same shop can do both, or perhaps you can suggest options.  The car has very nice (newer) burgundy leather seats, and I'd like to do something that would coordinate and complement the leather.