Unless someone is prepared to write out the full answer, I suggest an enjoyable read of Part M.
I think you probably can do what you want to do, but plenty of conditions apply; first one being are you properly qualified to do it?
Available at the EU bookshop, consolidated with AMC/GM, not including ED 2013/005/R which doesn't apply to you anyway. Snip at 18 Euros + shipping.
And I believe there's guidance on the CAA website, if you're prepared to dig for it, that would apply if you are in the UK.