the flat bits are deffo broken detent springs .its time to take your box out i,m afraid.some folk will tell you they can be replaced insitu,don,t even bother trying!the other bits are prolly bits of broken mainshaft.good luck.
have someone jiggle the engine crank from side to side only needs to be a bit. this moves the clutch so that the splines line up.you can sometimes do it just by moving the fan blades.while theyre jiggling you push the g/box.works a treat.
there's a hundred and one things it could by/might be,you are going to have to get stuck in and investigate.got a manual? you can't do much without one.
i've rebuilt it myself now for about £120.it isn't as daunting as made out,in fact it's really quite simple.no special tools required,and parts are cheap,mainshaft for example £29 +vat.i'd recommend anyone has a go.