Tamron lens... disassembling and mysterious spring

Hi

A friend of mine has a 17-50 Tamron lens that isn't working. The zoom
is stuck and doesn't move at all. He doesn't want to give to a store to repair
but since I repair musical instruments and have a lot of tools etc. he thought
to let me try it. I'm definitely not an expert with electronics but mechanical
things are usually not a problem. However, I've never repaired a lens
before.

Does anyone know about an online "guide" or drawing that can help
with disassembling the lens? Or any links or other suggestions?

Also, I
wasn't sure which direction to start from, so I started from the back. I removed
a few of the very small "horizontal" screws (lens back facing up) and moved this
part a bit. Suddenly this spring in the photo came out. I didn't even see this
spring before but it was out of the lens and I barely did anything. Any idea
where it belongs (sorry about the photo, I just hand held it at
1/15)?

Thank you for any help

I don't know but suspect it's the springs that keeps the diaphragm lever to close the blades when exposure happens.

Any help HERE? Or this lens with a similar problem HERE?

Thanks. I will look at that YouTube. The spring that is equivalent to the one in your first link is in place, so it is not that one (I assume that is the diaphragm lever spring, it is not my first langauge and I'm not sure about technical terms like those).