All good advice
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What shrimp did you have in the problem tank? Just cherries or some of our more fussy natives that HATE certain chemicals?
I would reuse everything you can out of the original tank the shrimp where in, their will be some degree of beneficial bacteria on everything and better to not lose any of it.
I would also save as much of the old tank water as possible and transfer it into temp buckets until you can move the busted tank and put the replacement tank in its place, then start putting all of your old water into the new tank. I would especially do this for any native shrimp like chameleons or blackmore river shrimp even the red noses, DAS are a bit hardier but would still appreciate the consideration shown to their water.
When removing the décor be sure to give everything a close going over visually and even swish the things around (gently) in the tank to dislodge any determined to hitch hiker shrimp. There is no worse sound then crunch as your foot finds a shrimp that was on something you removed from and tank and fell to the floor without you noticing. For small shrimp you can syphon them up and into a bucket, but you may find that they manage to cling on to the sides of the hose. personally I would carefully scrap all the substrate (Unless its sand and can fall through a net) to one corner of the tank and then use a net to catch the shrimp and transfer them either to a holding bucket which has some plants etc in it to keep them calm, possibly an airstone and a blanket over the top is not a bad idea incase they get a scare and try to jump for freedom. When shrimp are in the net be sure to place your hand over the top of the net when its out of water, some species of shrimp are shocking flippers and will flip themselves clean out of the net in a blink of the eye, while others are runner and will literally run for the hills (Typhus and riffles are bad for this).
If you really want to keep all the snails then you probably will need to pluck them off one by one. Or you could try using some food to get them to converge into one area and make it easier to collect them up. It sort of depends on the species of snail. MTS and rams horns will handle being netted and jostled about in a net with some substrate, while waterhouse and Essington snails can have very fragile shells. Nerites tend to just clamp down and are like limpets to try and move.
As for a heater, keep an eye on the expected weather, we are headed towards summer so HOPEFULLY your weather shouldn't be too extreme for the next few days or until you can get a suitable heater. I have used heaters too small for certain tanks but found if the fish where cold they just hung about closer to the heater and the warmth level they wanted, shrimp will tend to do the same thing.
And as already mentioned keep a close eye on any spikes in the new tank, shrimp can die so quickly from what started out as a simple issue, and as more die they had to the havoc for the remaining survivors making a chain reaction of more deaths.
