[C320-list] C320 Fuel Tank Replacement

[upwego]

I have just discovered a slow leak coming from underneath my fuel tank.  All the connection ports on top of the tank show no signs of leakage.  It may be a leak in the fuel tank itself. Has anyone experienced this condition and found another source of a leak that might be on the underside of the tank?  Has anyone removed and replaced a C320 fuel tank?  If so, any pointers that would be helpful or should I have it done be a mechanic?  I see Catalina Direct has a 29 gallon replacement for the 19.  Anyone tried upgrading to the larger tank?
Any advice or info would be helpful?
Thanks
Jack FitzgibbonHull #441, S/V wetted bliss