Does anyone know how this gun shoots? I've heard it has a weak receiver and that it is a waste of money! I am in the market for a 338 lapua
When it comes to a chambering like the 338 lapua, I only see one reason for having it.
It's an excellent long range cartridge.
To shoot long range you need an accurate rifle.
Accuracy is in each individual rifle (and also the shooters ability to shoot) not the cartridge. Having a 338 lapua will not make a rem 700 shoot any better or worse just like it won't make someone who pulls the trigger 10 times a year into a better shot.
To answer your first question, if you buy a Remington factory rifle you can expect it to shoot like a factory rifle. That means you can expect anything from 3/4MOA up to ???? (I've seen some pretty bad ones)

. If you happen to be really lucky you may get a rifle that shoots better than 3/4MOA but the odds are low.
To answer your second question, the action is just fine. If given a rem700 action w/lapua bolt face action, I'm quite certain I could turn it into a laser of a rifle. In my opinion the problem with most factory rifles reside in the barrel. Take it out of the equation and do some other things like truing/bedding the action and you would have an excellent gun guaranteed to shoot better than 3/4MOA.
Unless you go with a factory like a TRG42 ($$$$

$$$$$) then you may not get a gun capable of doing what the cambering was intended for. So unless your feeling lucky or are just one of those guys that want to own a Lapua for the cool factor, I'd consider having a custom build done or get a higher end factory rifle like the H-S or Sako.
For the money I'd go with the custom build to get what you want. The Sako and H-S are more of a sniper thing used for police/military. So if your serious about making the best use of this cartridge, then get a rifle built to do just that and not just something of the shelf.
Hope this helps.
Dave