It depends on who makes it. Some guns are plastic pieces of crap and others are metal and very durable. Either was the gun it self is good but I would consider getting an m14 instead because more people have them and know about them.
No
No company makes a spring action galil airsoft gun currently.
go for the m14, unless its cheap looking.
No, it is a cheap spring gun and could not be used in an airsoft match
A spring gun? It depends on how fast you can cock the gun. There is not a fastest gun.
yes
Never buy spring guns
No. even though some spring guns have great range, co2 allows you to fire more then once before reloading.
You can't without some experience in metalwork.
take apart the whole gun
yes
Neither