Battery tender and shore power

[outwithdogs]

Hi all!
Newbie here- we have been reading like crazy, so much great info on these forums, but I think we are stuck. I have disconnected the two batteries in our 2017 “new to us” 25’ FC, and attached one to a battery tender, after having pulled it from the box. We are hoping to prolong the battery life this way, when not camping. Is there any reason for me to have concerns about connecting to 50 amp shore power, so I can run a tiny dehumidifier inside, turn on lights, etc? Our AS is in a metal shop building, with blown foam insulation, so somewhat protected, but it still gets humid in there. We have our first trip planned for august, we want to have everything ship shape, and batteries ready to go. Any thoughts? Do I leave the AS unplugged? Will I fry or burn something if I plug her in? (So much to learn!)

Thanks fir any input!
Outwithdogs