20 years old...is that your age. ? If so well done for taking on such a challenge. I have a few years on you, well a lot really.
I re-timbered a Traveller about three months ago. I posted the progress on this forum.
There is a lot of associated work to do along the way. Most people do not realise this.
They just look at the finished timber work and think that is all you have carried out.
If you need any info just contact me.
As for treating the timber the other advice is correct.
Give the timber plenty of coats of 5 star Cuprinol complete treatment against fungal attack,wet and dry rot.
Danish oil is the very best finish you can give it. I personally always give my exterior timber a coat of light oak wood dye first to seal it,it also gives it a better colour...
Danish oil on its own looks too pale.
Avoid varnish. Any cabinet maker, furniture restore or joiner will tell you Oil is best for outside finishes.
The interior timberwork you could strip back to bare ash and then you could give it some coats of medium oak beeswax...a lovely natural finish.
Cut back the timber with a scotch pad between coats ,wire wool was used in the past,I used it for years, but things have moved on since the invention of new products.
The trade use it all the time working with joinery finishes and the car trade for giving paintwork a good key.
M.M
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Thankfully a small socket came to the rescue... 
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