I would bring them up slowly. If you have a second shelf I would place them on that while heating up.
Over on a wood fired oven forum I just read that a guy had one of his floor tiles, made of fire brick, explode due to moisture in the tile. He had not used the oven for 3 months or so, but that was enough.
If you have it wrap your pan eniterly in foil, fill it with playground sand, foil that and heat it. Just like a heat sink in a cooker.
KCBS CBJ 9831
Large Spicewine, Backwoods Smoker (Party), WSM, Oklahoma Joe's Offset, Wood Fired Oven