。
It's best if you go and look into it in person as much as you can.
Literal
As-much-as-possible you in-person [subj-が] go-[and-て] investigate [better-たほうがいい] [emph-よ].
できるだけ 'as much as possible' modifies the whole advice. 本人 'the person in question / oneself in person' emphasizes the agent's direct involvement — not a representative. ~たほうがいい 'it's better to X' is the standard advice/suggestion frame, formed from the past form + のほうがいい. The sentence demonstrates how Japanese stacks mild suggestion modalities on a neutral infinitive.