Unless you decide to upgrade the spring, there's no need to buy sears or a trigger box for a while. And even then, the trigger box is sturdier than what most people would give it credit for. I've shot 10k+ rounds with the stock spring, 5k+rounds with an m170 spring both using the stock trigger box. I then decided to switch to a zero trigger. The stock trigger assembly is still working btw.
In case you decide to buy the Angel Customs sears... DON'T. It will not fit properly without modifications.
An alternate solution is to buy a new stock trigger assembly ($30) if for some reason the sears wear down or the trigger box snaps. Do this if you really don't trust yourself replacing sears or opening the trigger box.
The biggest issue of the gun is the hop up chamber. It's awful for several reasons, but I won't get into that.