Weathered cedar looks good yes, but you aren't going to get that weathered look indoors with out the light. You can make artificial weathering DIY to get that silvery gray look but weathered cedar is far from the warmth new cedar.
Jointer is used to joint edges and face of a board. Used to square stock. A planer is used once you get a squared face from the jointer to plane stock to desired thickness.
If the stand is built from 2x4 no need to go with 3/4 thick ply. You can go with 1/4 veneer with no issues. I used one sheet for the 75 gallon stand I built and I think it was around 45 (cherry). Likely going to spend more on cedar based on the last cedar I bought to build our bench/privacy screen on our patio. Also most places will have a scratched, bad corner, etc.. bin and veneer ply always makes it way there. Will save a little because will need moldings to cover stuff up.
This stand used 4x4 and 2x4 frame. I used half lap joints on the 2x4 and 4x4 connections. Dowels were used on the vertical 2x4. I used 3/4 for the top and bottom (because needed to thin stuff out of the shop).
After that I used 1/4 thick birch veneer ply and a quality glue to cover the inside of the stand and a few coats of polyurethane. I wrapped the outside stand in the 1/4 cherry veneer and took a few boards of cherry and made my moldings to wrap the edges and make door frames.
Couple coats of poly and let nature takes its course on the cherry and it will develop the rich color.