you'll need to change the lock cylinder and I don't believe this is available anymore as a rebuild from bmw. I do believe the repair kit is still available. it's in around 70+ give or take from the dealership. Otherwise get a used trunk lock and deal with having a separate key to open it. I can probably get it to open if it is seized shut. you'll need to swing by my place- hypothetically speaking. LOL..
I think I've had 14 bmw's in 4 years.
2 IX's -sold and parts
2 325i 4 dr - sold
4 318is all white - sold and parts
1 87 325is red - parts
1 89 325i vert grey - parts
1 90 325is white - keepin
1 87 325i vert -red - keepin
latest addition 1 88-325is red - parts
latest addition 1 89-325i vert - white -fixin/sold
latest addition 1 92-318i vert - blue - parts
latest addition 1 87 325is blk - parts.
latest addition as of 2013-Gold 87-325is auto! it's a keeper!