I have a new job, and the plan is to replaster the 50,000 gallon pool, and then also buy 2 new triton two filters.

Pool needs new plaster, but filters are only 20 years old at oldest, pool is a holiday to hoiday summer pool.  Ive been told one filter has slight leak at drain plug, no filter sand in the pool, i don't think the filters need replacing.  Median probaly should be inspected, and possibly replaced (stuck is lid another issue, already broke one handle).

1st question the bells themselves should be fine?  20 years old, always stored inside not heated, but only colorado winters

How long would it take to rebuild the insides of a single triton 2 bell?  It looks pretty easy but takes some time, if I need to preplace all the sand and have a few broken laterals. 

If I need new sand, wouldn't it be better to wait until the replaster job is set?  I am thinking that by waiting for the plaster to fully set, I won't have the plaster dust intermingled with the new sand forever?  Is my thinking here sound, or am I being over paranoid.

Any thoughts on all the other medians like glass, the cotton ball thinngs or ocm's product that OC-1 median?

Thanks in advance