I have a Stock WRT 3200 ACM, just want to make sure i can just install new build of OpenWrt for my device ??
You can search the Table of Hardware to see the current support
It looks like there may be various models, give that "v1 (rango)" is called out on the non-standard page for that hardware, https://openwrt.org/toh/linksys/wrt_ac_series
The "final word" for "official" releases is what is available for download https://downloads.openwrt.org/releases/18.06.0/targets/
so just flash the current build of OpenWrt like i would do a stock linksys flash ?
I'd confirm that you have the proper version of firmware to match the version of your router first.
Then you'll have to figure out from that page what the proper instructions are. As that page is inconsistent with other device pages in both its formatting and advice, if you have any questions, you should contact the individual who has taken control of that page.
If by stock you mean your rango is running OEM, use the factory image, if it is currently running DD use the sysupgrade image, but do not keep your config.
i did not put DD on the 3200acm , it is still running the stock firmware from linksys, i want to be able to increase wifi wattage and use to connect to a vpn.
You will not achieve any change/increase in power as it is fixed in the eeprom on the rango.
so the OpenWrt does not allow changes
well, the OEM does not allow any change, as they opted to fix the power table in the eeprom, so here is where to raise a voice, not that there is much that can be done.
You can adjust the power; but you cannot adjust it out of the OEM specifications. Because as @anomeome said: