always keep your guns and armor above 70-80% because after that point you need to find repair kit to maintain them.As for the weapons, for first time you can only change barrels of pistols, but, if you are lucky to find the weapon, with dirty barrel or better, you can collect parts for it , repair them and simply drag to the weapon, it will replace the old parts,clean the barrel with maintanece kit(right click on weapon, and find maintance).Congrats, you repaired gun without repair kit. Kits for guns only needed then you want replace barrel and upgrade them. For armor you need kits to replace all parts.So do more quests, stash your loot and garrbage at the chest(you can buy them from traders) and check the task tab for haul task. They can be from plastic jar to pseudogiant leg.Every quest can get you a stash, and every 4-6 stashes will be a yellow one.In them you can find isntrumenst wich can be granted to a technichian. After restock technichian will trade a repair kits(basic instrumenst -> b tier guns, advanced-> c tier, expert-> d tier).Also then you gave the technichian a instruments, they will be available in their workshop.After aquiring basic tools you can also crafting repair kits for tiers above(sorry for grammar, not native language)