It may be possible to get a trailer in a 7' door by letting air out of the tires
, or a spare set of rims with no tires
. I have 4 campers here in storage, only the Uhaul
is outside. I put mouse traps in all of them, the spring type and the sticky pad type. Check them occasionally. I'm not sure about covering a trailer with a tarp, it may hold moisture in, or a plastic tarp could stick to the trailer or transfer color if in the hot sun. Some people like to jack up the trailer so wheels are off the ground and cover the tires
to prevent sun damage. At least put boards under the tires. Remove battery
, be sure all water is drained.