Does this answer you first concern?
Manipulate[
t = Quiet[ Check[Import[url], {{"error, please provide a valid link"}}]];
Pane[TableForm[t], {Full, 300}, Scrollbars -> True, AppearanceElements -> None]
,
{{url, ""}, InputField[Dynamic[url], String, ImageSize -> {500, 35}] &}
]
You can achieve this in many ways, the question is what is the final goal, for more complex UI please consider writting everything in terms of DynamicModule+Dynamic instead of Manipulate.