If you already have a very heavily modified runuo server and you are not up for the task of re-doing scripts or attempting to merge scripts then I would suggest you stick with runuo as to not cause an extended downtime on your shard. Gain more knowledge on C# and how it works along with how runuo/servuo both work the best you can and then make an attempt on the side at trying to convert to servuo.
I converted my heavily modified runuo server over to servuo a few months agos, The thing that made it a breeze for me is that i kept everything i did very, very well documented. I keep a in detail changelog and I keep unique keywords commented into my major scripts that i note in the changelog. So every major addition or edit i've done I can search for the keyword and instantly find what I know I've done.
It can be difficult if you haven't documented your edits to quickly and almost seamlessly convert. So I guess after this long winded post I suggest to you that you should begin documenting your runuo shard's edits or just take a day or so and go full force at it. Servuo is the future in my opinion and it will have better bug fixxes in the long run.