When you get to Rambutan ask the front desk for a copy of “Siem Reap Angkor Visitors Guide” and it will give you a lot of good information on temples, guides, and lots of other activity. Rambutan staff can also help you arrange tours etc. They are quite good. Here is a link I found that might be useful as well but I have not used the guides yet so I can not report on their quality.

http://www.khmerangkortourguide.com/...uide-list.html

Another option might be Siam Guides but I have emailed the Siem Reap guide twice with no response. Not sure if it is a technical problem or if they are just slow to respond to inquiries.

https://siamroads.com/cambodia-siem-reap-sareth/