I am not an AR guy. My experience is with wood sport rifles.

I have a perfect Colt AR HBAR MT6601 post band, no bird nest with the handle built into the upper receiver. I took it to an AR shop and they advised me to change the receiver to a flat top and mount the scope. Could you guy's comment on this modification? Please feel free to comment on all aspects of the build, effecting value of original AR. The type of scope mounts and scope size? Is there any modification to the front sight with a scope?

I would like to keep as close to all Colt as possible. The only reason I'm looking at a scope is my eyes are 62 years old.
All advise welcome.
MM879