hello and happy thursday, Another suggestion would be to replace your heads with remanufactured ones. You can easliy spend a bunch when having yours reground and new springs and valves and all. Because if you are taking both of them off to have it done you better use all new parts, not just replacing your broken valve. Guides, seals, valves, springs, keepers and ll will add up not to mention labor. Germanstar.net has your heads for $400-$500 or so for each. And, yes, I would replace chain guides as well. good luck and get that thing back on the road!
Have a special day,
Goody