Where to start...have premium easements to digital/non digital signs

Hello and thank you for any advice in advance. I am the owner of 2 easements to signs located on very busy interstate highway…it is a premium locaton. One sign there now is digital and one is not. There are distance requirements between digitals and I have the only one permitted in the area. I know in the area many companies are buying these easements outright or some sort of share arrangement in the sign. My preference is to find a company that would like to buy them outright and get out of the sign business. I have some leads on these companies and some have contacted me. Now I am more ready to talk to them but wonder how one goes about establishing the fair market value of these signs? Someone suggested an appraisal. Based on past experience with land these appraisers are very expensive and I am not sure if this would require one or not. I need some solid information to even know if these companies’ offers are worthwhile. At this point the lease is old and close to renewal and it was based on non digital numbers and therefore the money coming in right now is far different than a lease negotiated for the digital. Any direction you can give me would be helpful…these are valuable assets and I want to make the right decisions. Holding on to them is an optin but not my first choice. Again thanks for any ideas…and if an appraisal is what is required I will do it but seems like maybe there is another way.

Just a quick question, have you considered upgrading both to digital and then getting rid of them?