Filled out the online forms on DNM website, attached the required documents like my CV with university studies and work history, proof of income, explained my work to them in the letter of presentation, paid the fee and submitted it. Then they sent it to the local consulate (Montevideo) who the next day told me I had to pay them another fee to pay within 24 hours. I did so and the next day they emailed me the visa. All up it was about $250 USD. It could be that some consulates simply take longer to process these requests, which would explain the problems others have been having. I can only vouch for Montevideo.
The visa seems to be renewable for another month according to the DNM decree that created it although I have no idea if anyone at migraciones would even know this since it's so uncommon, so it might be hard to convince them. Regarding tax obligations I have no idea.