I took the old spring out. The guide was difficult to get out because the tube was filthy.
It was packed with crusty bits of shotgun powder etc. The tube was corroded so I sprayed PB Blaster in it and worked the guide out with a pair of channel locks. Took a little twisting and turning.
Cleaned the tube with a brass brush (20 gauge).
Then ran lots of clean patches through.
Put a new spring and guide in. Cost less than $10 for parts from Brownell's.
Reassembled the shotgun and it's faster and much stronger.
I'd like to thank all who contributed to my success at repairing my own shotgun.
Probably saved myself a bit of jingle for some ammo!