Welcome to TFP! Good to have you here
If the test kit has been in the shed, a lot of the reagents have probably gotten too hot, although not all the reagents are killed by heat.
If it was me, I'd order a full kit from ClearChoiceLabs and then do some cross-checks to see what is still usable from your K-2006 kit. You'll be learning what is compatible that CCL can supply, because it's quite expensive getting Taylor refills here. You'll use it all in a year or two anyway, so you won't be wasting anything. In the meantime, don't throw out any of the Taylor bottles cause some can be refilled with CCL reagents.
Compatibility chart is here:
Test Kit Reagent Compatibility Chart Clear Choice Labs
and CCL is very helpful on the phone as well.
You'll find stabilizer in Coles or Woolies sometimes, but Bunnings and Pool & Spa Warehouse have been best for me. I mostly just buy hydrochloric acid ($15 to $16 per 5 litres or $52 for 20 litres) and a couple of 15 litre of jugs of chlorine per year (around $24 for the first one including deposit, then $13 for a swap refill). I haven't found cheap bleach like they have in the States. I spent $230 on chems last year.
Good decision, mate! Those pool $tores have nice people, but I think the chem companies lead them away with the pixies when it comes to pool chemistry.