Volvo: 1986 760 turbo sedan, car stalls, engine mounts

Question
When cold the car seems to have a problem up-shifting.  But after about five minutes it is less dificult and only has a little trouble getting into 2nd and 3rd. Also, at seemingly random times the overdrive has come on without warning and manually I was unable to turn it off after a minute or so.  the car has stalled on me a couple of times while driving. are these problems related?  I have also noticed that when in park, the car sounds as if it is going to die, although it never has.  the tachometer sways. i try to never leave it in park for long because it goes from a normal sounding idle to the disturbing noises heard before your car stalls. i am a starving college student and the mechanic has recomended a new muffler as well as flushing the tranny, new engine mounts, and new brakes. can i get away with not getting some of these things replaced until my next paycheck? im pretty sure i am gonna flush the tranny and get new engine mounts since i can actually FEEL the problem, but are the brakes and muffler really do or die?  I am sending it in again to get an internal diagnostic soon to find out more about the overdrive problem is there anything else you suggest?

Answer
Nick,
Flushing the trans will probably help the shifting and the engine mounts will smooth out the idle so you do not feel the shake. Brakes you need them, are the pads and rotors completely worn out or do you have some time left? I always give brake percentages so the costumer knows about how long is left. Have them checked that way so you know. Exhaust will get into the car if there is a leak and that
Carbon Monoxide is deadly, again find out what parts are bad and look to see, ask the tech if there is any time left on the  exhaust parts. Do you smell exhaust and is the car loud?
If the idle is up and down there is a problem and that will take some diagnosis to find, maybe that tune up will help. Have the shop also look at the throttle housing to see if it is all cabined up and needs cleaning. Often times that is the cause of any stall and idle problems.