1. the Saiga .308 sporting rifles do not require the bolt hold open to function safely. i used forceps to hold the spring in the correct orientation, and install the hammer, then position the trigger nearly in the pivot pin position, then while holding the hammer, place the spring and slide the pivot pin in from the side with the hand holding the hammer down. another technique which is simpler is to use string to thread and pull down on the spring for tension during installation, but i personally find that more annoying.
2. the Tapco G2 trigger is not intended to be used on the .308 Saigas without modification because the .308 safety lever has a shorter tab due to the original position of the trigger in the receiver. i generally do not modify these parts, but instead replace the selector lever with one from a standard AKM. you shouldn't need to use the original safety at all.