How can I update my wallet without losing my coins in my current wallet?
Your best bet is to quit the client, delete the block chain, and restart the client. You may have lost coins sent to you in the last 10 hours or so. If they came from bittrex, you will not have lost them. If they came from dedicated, they could be lost.
Block chain data are kept in
blk0001.dat
database/
db.log
blkindex.dat