I brew similarly to how you plan to BIAB, I wouldn't bother with the hop sock myself. I use pelletised hops and they break up almost instantaneously and they settle fairly well with a whirlpool at the end of the boil.
I use a simple thermometer (
similar to this one) with a bit of string tied to the top of it, then I use a bulldog clip to clamp it to the side of the urn. This way I can keep the lid on during the mash and lift the lid a bit to check the temp when I want. Also, I have a thermometer for other use as it is not a part of the urn.
Sorry, I don't know about the weldless ones.
Apart from that you will need a paddle to stir in the grain and to create a whirlpool. I just use the plastic paddle that I got when I bought a starter kit (the kind that has everything needed to begin kit brewing).
You may want to get a metre or so of tube for running the wort into the cube. I use a metre of this
silicon tube from CB. This is not for any Hot Side Aeration issue (realistic or mythical, I don't know either way), it's a safety issue, basically so I don't splash myself with bloody hot wort and also so that I get the wort where I want it: in the cube. When attaching to the urn I also use a hose clamp that I got from the hardware store, the kind where you can just screw it tight and then loosen it for removal. It's a bit of a tight fit, but it does go on the tap with a bit of effort.
If you don't have any already, perhaps order some grain for your first brew?
Note: while the urn will probably boil fine for the first few brews, it won't continue to do so. There is a thread about the urn you may want to read. I own a 40L Crown with a concealed element and rather than modifying it I purchased a stock pot (60L) drilled and fitted with a ball valve and eletric element for boiling from Craftbrewer. (Let me know if you want more details).
Thread about the issues
The reason I don't mod my urn.
Also search for Crown Urn and have a read.
I use my urn to mash in, I drain that to the 60L stock pot for the boil and I drop the wort into a cube from there.
I hope this helps.
:icon_cheers:
EK