We will be having new hardwood floor installed on entire first floor of older home in New England. We added on several years ago, leveling plywood subfloor with existing birch/maple hardwood in bad condition in the old part of the house, and covered with carpet. Our questions/concerns:
1. Can we install the new floor over the old hardwood? (height is not an issue)
2. We don't have air conditioning; how long should the wood acclimate before installation? Our project is planned for late april/may before the New England humidity sets in - any issues?
3. Given lack of air conditioning, is there any advantage or disadvantage of unfinished vs pre-finished? (we are planning on unfinished) Any wood types we should absolutely stay away from?
4. Given the conditions, is it better to go with wider planks or narrower? (we like wider or mixed, but does it affect the stability or tendency to shrink and expand?)
5. My husband is concerned about staining a floor in terms of potential scratching and ability to do touch-ups, but we're having a hard time choosing a wood that will give us a medium color (in between say a red oak and cumaru or brazilian cherry) with just a clear coat.
Thank you so much in advance for any help and advice!!

I am having Hardwood installed and my subfloor is 1X8 pine boards
Which old hardwood was nailed down to it, can I put luon sheets on top of the 1X8 s then the hardwood?