Re-sealing an old tank?

[kyl]

I'm currently in the process of converting an old trimmed Oceanic Systems 58gal (36x18x21) tank into a reef setup with a sump for my parents. This tank has a sale date of 1998, and has been wet for the last 10 years with zero leaks. I just got the tank dry today to start cleaning it up and most of the interior silicone seams have gunk under them which you can slide a finger nail into.

Aside from aesthetics, am I wrong to think that this will impact the integrity of the tank given the reef setup will have power heads in it? I'm not averse to re-sealing the interior seams, or should I just leave things alone?