Wow, your review is way off base about why the Oldsmobile brand/badge was put to rest. You should take it to a different mechanic. All GM vehicles around those years had wheel bearing problems, but this is the first time I have ever heard of it wearing out that quick. It sounds to me that the mechanic is ripping you off and not replacing the bearing with good quality OEM replacement, or is using used ones, or is not replacing the entire wheel hub assembly, and just replacing the bearing. Take it to a different mechanic, and use the original brand GM used, which is either AC Delco or Delphi; more than likely AC Delco.
Go to an auto parts store and have them order you a new driver's door rubber seal; easy to replace and cheap, and that will fix the leak.
For the key not coming out of the ignition, it is either the shifter assembly isn't going all the way into park, or it could be the key lock cylinder or a solenoid.
For the brakes needing replaced every few months, it's either you are buying very bad quality brake pads, or the rotors need to replaced, which should be done every brake change, or if you have uneven wear, then you need new calipers.
All the things you mentioned don't make it a poorly manufactured car! You have 150,000 miles. That's a lot of miles.
As for the bad fuel economy, it is most likely a dirty fuel filter, or it just needs a full tune up, and/or your tires are not properly inflated.
Take your vehicle to a different mechanic, preferably a certified GM mechanic.
Hope this information helps you.
The car I'm talking about has only got 150000 kms, not miles, and is a complete lemon. Just had to spend 500 on new brakes and rotors.
I have a 2006 Honda Civic, it has 186 000 kms, never any trouble besides oil changes, which is regular maintenance, and replaced brakes once. Drive it daily and do a 500 km trip each weekend.