Hi from a newbie to this forum

[Sinterior]

Hi, I just joined the forum tonight because DW and I are seriously looking at an '09 Montana 3400RL Anniversary edition. (the floorplan fits us to a T) It's only been used for 3 months and the owners traded for a park model. I know and trust the dealer, having purchased from him before, a different brand, so that's not an issue, but they don't sell Keystone products.
I know how to do a search but didn't find any quick answers, so.....please bear with me.
Are there any common problems with this model? Or Montana's in general?
Are disc brakes a worthwhile upgrade after market?
Any suggestions on what to look for before buying?
I know that many years ago hydraulic slides were a big problem, but a lot of manufacturers seem to have gone this route again...have these problems been resolved?
My current fiver is a Travelaire Genesis, basically identical to a Titanium (Glendale) which is now out of our price range, only built in Alberta, Canada. We have had basically zero problems with our fiver and want to go bigger, and are believers in preventative maintenance.
I know I have to get another TV, upgrade to a dually....should have done that right from the bat, but, who knew that we would want to go from a 1 slide 10k fiver to a 4 slide 15k+ fiver! Boat people call it two foot itis.
I guess it's called retirement.

Thanks in advance to any responses.

Peter