I'd go for the ethernet cable option. an access point will produce a signal as strong as the main router. The ones I've installed have all been plug and play. You will need a crimping tool to attach the plugs on each end of the ethernet cable (and the plugs or course). I got a really cheap one off ebay which has proved satisfactory for the few times I need to use it. Pretty much any access point will do what you want. I have used these in the past. Example of crimper here.
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