Sorry that the estate people thought they had more than they did. Most times they don't sell the 'extras' with the machines. Do you have the hoops?
You can use any type of thread in this machine. For regular sewing you use what ever you have ever used. Of course there will be some threads that 'fuzz' up the machine just like other machines. As far as embroidery any rayon or poly embroidery thread will work. Embroidery thread is usually shiny.... They promote the Brother brand in these machines, but I never found a difference between Sulky, YLI, Maderia, or any of the other brands in my machine (2002D, which is a newer version of the 8500). As far as maintenance, with an embroidery machine you will want to have it serviced at a certified service store. If you mess up the embroidery arm that needs to be re-calibrated. As far as just regular oiling and cleaning---these machines need to only be cleaned out real well. With the drop in bobbin you need to take the feed dog plate off and clean out that area often (between each project and if you think there is a problem). You can put a single drop of oil in one of the holes in the bottom of the plastic bobbin case, but don't over do it. That is all that I have ever done to my machine.
As far as the cards are concerned you will need a card reader with a blank card and a software that will load the designs onto the card from your machine. There are a lot of different software programs to do this. There are 2 types that I know of... the ones that you can digitize pictures/jpegs with and the ones that just take a certain design that resizes and puts it on the card. You need to google/bing to find sites that sell these things. I know there are several online stores that still supply these older machines.
Good luck and happy embroidering!