A trip to your local Homebase/B&Q should furnish you with materials to repair your greenhouse.I have repaired sheds which others have cast aside as being past it yet they are still giving stirling service. To repair the soft wood I believe Cuprinol have a product which when applied to the wood hardens it. If the silicone is sound, leave it well alone. If any is coming away, apply more. To finish the wood off, apply Cuprinol 'Garden Shades' available in a number of colours. All my sheds are in 'Somerset Green' a nice dark shade. This covers better than any other product I've tried and the brushes wash out in water, always a bonus, and the finish will repell rainwater.