How much of the wall to open and patch is another question. Only someone on site can tell for sure. A photo would help. Perhaps it will only be possible to replace the valves by cutting open the "drywall" or whatever your 1938 house has as wall surface. It may be possible to have a set of dual shut off valves; there are ways, that experienced plumbers know. E.g. installing an "offset" or moving the pipe by an inch without stressing it. Besides, how much distance is deemed by you to be just slightly too far apart might not be too far apart. Copper was the material for your pipes in 1938 but what material gets installed today is up to you or your plumber. Which fittings or adaptor to use is another question. If the new valves are to be soldered, this opens another batch of "things to know". There are still many little things to know, katsmah, but if you read a lot you might be able to get a whole lot more comfortable with the work involved. A single device can be purchased that one can probably install all by oneself no matter how many left thumbs one has: a combination sharkbite / hammer arrestor / shutoff valve . After web searching, call the Sharkbite company for guidance to figure out what product. A "master" plumber can work with pipes that still have water trickling down. The drier the better. The whole house water has to be turned off and the water in them has to be drained from all the pipes before cutting into them to replace a non-operating valve. It can happen that this takes a fair amount of time. If you and a handyman do this valve replacement, it will help your handyman helper if you drain the pipes before she or he arrives on the scene. Nothing written in this post is intended to contradict manhattan42's statement. The job will cost what it will cost. To be more certain of success, hire a plumber who charges a high hourly wage. On average when you compare a low-price and a high price plumber, the latter will be faster, more efficient, making wiser choices, being smarter-for-you, installing everything in a better quality way with better workmanship. Hth

The pan has a threaded connector to allow the pan to drain into the floor drain. The threaded connecter sits proud of the bottom of the pan by approx 1/8" so if I just pour water into the pan now and then, most will drain out but not all since the threaded drain creates a small lip (see attached photo for example. It also creates a potential opportunity for a leak which is why I'm not crazy about the idea of just pouring water in the pan. Instead I may snake a small 1/4" or 3/8" tube into the drain and have that run under the washing machine and up the back so I can fill it from up top and keep the pan pretty much dry. Anyway, I'm surprised I'm having to go through such a DIY solution as it seems like this would be a relatively frequent problem for this type of floor drain/pan setup.

I guess I’d like to implement the best solution for any possibly scenario. I would have to speak to the plumber and/or the contractor to understand exactly what goes under the tile or can go under it to make it waterproof.. as of this moment I don’t know what the plan was. In my mind it would be like the shower, how they put down that black vinyl waterproof barrier, but maybe that’s not what they do...? I have bare plywood right now so I can do whatever is best- just have to understand what that is, so I’m looking for some input from anyone with experience. I’ll have a shut off valve for the water supply, so that should take care of any major water supply issues (if I remember to turn it off), so mainly a backup plan if the washer overflows, leaks, or malfunctions in some way when draining (plumbing backup?)

"For future reference- if you have a wet/dry vac, you can often use it to suck a clog out of a discharge pipe." And you may not want to know what else you'll suck out of a sanitary sewer! I'm not very squeamish, but i'd prefer it flow away from me. If you want to save money get the pro quality snake from a rental place. It's not too hard to do. Most folks, understandably, are happy to pay the roto rooter guy.