BMW Repair: 03 m3 ac blowing hot, vacuum leaks, r 134a

Question
Hey Evan, I have been browsing the foum here, and have a question about the ac system.Its been blowing hot, especially on the passenger side, and slightly cooler (but not cold) on driver side. Its also hissing pretty loud. I am pretty sure my hoses have leaks (according to the dealer). I guess I have a few main questions
1. You said to avoid r-134 w/ sealants, and Don said to use them, is there a reason, can they damage anything?
2. How can I find out what hoses I need for an 03 m3 to replace? Internet left me unanswered.
3. Do I need to flush the system out when replacing hoses or can I just replace them/charge the system?
The dealer quoted me over $1000 which sounded way too high to me, and Ive always preferred to do the work myself, just never messed with ac systems before. Thanks for the help, David

Answer
David sealants in A/C system damage the equipment used to recover/recycle/and recharge your A/C system. I haven't seen them work. A/C systems are not designed to use sealants and can cause adverse effects on Expansion Valves and Compressors. You must completely evacuate the system before performing any repairs. You don't need to flush the system out, but it needs to be vacuumed of all air after relacing parts. Vacuum should be held to see if the vacuum leaks out. Then the system should be recharged to factory capacity (Green label under hood). In order to figure out what hose or component to replace you need to find the leak. Use either refridgerant oil with dye in it or use a refridgerant sniffer to sniff for leaks. Condensers in front of the radiator are the most leak prone due to constant road debris. Look for any oily parts or hoses. R-134A should be properly disposed of and not vented to the atmosphere in any case.  
-Evan