first, welcome aboard
second, be prepared to spend a lot of money to restore your boat. in addition to the upholstry, most likely the transom and stringers are shot. Free boats are the most expensive to own, with "super cheap" boats being a close second.
this is an expensive time to restore a boat as the cost of materials is about 3X it was 15 months ago. for your 19' boat, you are looking at about 20-30 gallons of resin, about 40 yards of 1708, about 30 yards of CSM and about $600 in lumber for the hull. what used to be a $2500-$3000 hull restoration and a $2000-$2500 upholstry restoration is now closer to $4500 for the hull and about $3000-$4500 for the upholstery depending on how much you do yourself.
pull the drive, pull the motor and do some test drills in the stringers and transom.
at the top of the forum are the stickies. the 4th one down has all the info you need to restore a boat
look at links 14, 15, 18, 2, 3, 4a, and 4b in that order. read every comment, watch every video, etc. it covers most everything you need
to change oil, it helps if the engine has been run and is warm. then you use a marine oil pump to suck oil out of the dipstick