The extractor and its spring have nothing to do with ejection. The extractor spring is there to return the extractor to its 'start' position after the case head is under the extractor and after ejection. It doesn't power ejection though.
"...Spring has seen better days..." Maybe, maybe not. $10.80US for a new repro($15.70 for a brand new one. $13.50 for a used unknown condition one.) at Gunparts.
"...long enough to hit the ejector screw..." OAL length doesn't matter. Case length does.
"...it's not ejecting spent cases..." It's most likely that you're not operating the bolt with enough, um, vigor.
Oh and the only difference between a Mk I/Mk I* and a Mk II is where the trigger connects to the receiver.