What size line wrenches will I need to swap it out?
The fittings all seem to be metric. 13mm and 11mm have been mentioned. I would just get a set with at least 14mm to 10mm. Most sets are 3 or 4 wrenches which cover 6 to 8 sizes.
Any other tips are appreciated as well.
As much as it sucks you might want to go at this slowly. You have identified a cylinder leak so first you need to know if you have the small(9.5), B4U(11), or wagon drum brakes(11). Each seems to require a different brake cylinder. Shoes to match. Good parts places will have hardware kits so you get new springs and that little shoe retainer part that always goes flying away. High temp brake grease for where the shoes touch the back plate.
Put down some cardboard or paper so cleanup will be easier. With the car jacked up get the drums loose. Back off the shoe adjuster. If the drums have a ridge they will need more space. If the drum is stuck to the axle shaft oil, heat, and pound till loose.
For the brake line fittings same thing,oil, heat, and pound till loose. Brake dust bad! Do not breath it and do not use a good vacuum to clean it up.If the steel line starts to turn with the fitting quit unless you have replacement lines ready. The more rusted they look the less chance you have of not twisting the line when you turn the fitting.
Take pictures of each side of the axle's brake hardware they should be different. If some idiot has installed the parts wrong and you copy it you will have problems. Get the brake adjusters set close to the drums.It would be good to have a service manual or a how to book photo copied so you can get it dirty.
Read a book, google, or watch a utube or two. It is not rocket science but it does need to be done right.
I have skipped a lot of little steps that need to be done right. The factory service manual is always the best place to start.
This site has a lot of information on rear disk brakes. You might try the Longroof forum(wagon) to search for drum questions as they never came stock with disks.