I am in a predicament. I am not allowed to leave home for long periods of time due to health issues, but I urgently need to update my documents, which are about to expire.

I don't think there's any need for that, because if you can send a postal letter, then everything is fine. I recently applied to a company that works with the Russian consulate to get zagranpassport. I mailed my documents to them and then after some time I got new documents. It is very convenient and, by the way, at an affordable price, which is important.