Fish problem. Dropsy?

I suspect my chocolate oranda has dropsy.

Just behind his left gill is all risen up.  I haven't noticed it
recently (so in the last two days), and it looks incrediably painful
for the fish.

I am worried and also quite poor.  Tomorrow I have several deliveries
due, but I suspect that they'll take second priority.

I'm reading all the sites I can to get a fair idea how to treat him.

I do have a normal salt level (not sure the accurate reading) but
should I transfer him to my very old tank (the 1 gallon transfer tank)
with some declorinated water and epsom salts? I have just purchased a
new airstone, pump and thermeter.

A step by step guide would be appreciated!

I will follow this post with a picture as soon as I find a chemist to
buy batteries for my camera.

The real question is, how long have I got to treat and restore him to
health before he dies?