RV Repair: RV toilet/tank, wastewater tank, rv toilet

Question
The slide valve to seal the wastewater tank does not seal. It slides but I cannot stop waste from discharging. I have a 74 Silver Streak (28 foot Continental)and have been told I will need to drill out the rivets on a bottom panel to access the valve. Is there an option to access this from the top side by removing the toilet? Any suggestions on trouble shooting this issue? Would appreciate any heads-up on this process you can offer. I a reasonably competent home plumber/carpenter and do a large majority of home and auto repairs.
Thanks in Advance,
Dan

Answer
Dan,
    Unfortunately, what you were told is correct.  These type of repairs must be done from under the unit.  If your unit has an enclosed underbelly, this will have to be removed enough to access the valve location.  Some valves used in that brand were riveted together, some screwed, and let's hope that it is the last... bolted together with 4 bolts.

Garry