1. It won't go bad. But over time the color might fade due to degradation by either sun light or heat.
2. Hard to say depending on the kind of dye you use. But if kept in ideal conditions it should be fine.
I would suggest using either acylic cement to fuse the plastic or a silicone based adhesive to prevent any form of leakage.
When in doubt, just take the next small step.
With that next step take a deep breath. It calms the mind.
When the mind is calm you realize the best is still yet to come.