Key Fob Chewed

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Need some help the title says it all really
My 8's fob has been molested by our Puppy Damn dog has chewed my shoes too!
I have all the bits but the fob doesnt work now and having taken it apart some of the inside electrics have seen better days!
My 8 has the advanced key with keyless go and the finger print thingy.
Whats the best solution is it an expensive trip to the dealers?
I have read conflicting things and reports about re-programming the fobs listed on the bay having spent the last hour searching. I have the blade which I assume could be refitted to a new key?
Luckily I have a spare so am still mobile but want to get a second one for safety.
Any help or pointers or links to buy the right part etc.
Much appreciated
Cheers
Glyn