I had a similar leak recently (3 months ago). I used Wynns PAS stop leak and it has worked so far. It took about 4 days to work fully so give it some time before you give in.
I'd certainly go for sealing tricks first and leave doing the box seals till the summer!
Removing the drop arm is a bar steward and I ended up paying the garage a tenner to get it off, after trying pullers, heat, violence, etc. Having got it off I couldn't get the ball joint top cone out as it was so corroded so I ended up with a new drop arm (EBay - 99p!) and so I could have used plan B (the angle grinder) and saved the tenner.
Here at LandyZone we have plenty of very knowledgable members so if you have any questions about your Land Rover or just want to connect with other Landy owners, you're in the right place.