First and foremost enjoy your experience and congratulations . My wife and I recently purchased a 17 Newmar DSDP 3724. It has 4 slides, 450 hp, and it really just fits us perfectly . Not too long but big enough for us to travel and we love it. We have had 2 issues but it only has been on 3 short trips ( each trip less than 300 miles). 1 issue was hose clamps on the transmission coolant hose and a bad gfci in the kitchen which resulted in the tv not powering up. I was able to fix both myself with the help from Newmar customer service. The last issue was a recall on a potential power steering hose however inspection at my local freight liner resulted in no issue. We were first time buyers so it was new to use. We considered Tffin and American Coach. Newmar made it easy for us because the floor plan. Ordering was easy through Mt. Comfort in Indianapolis and it took about 2 months to get the coach. Although we didn't ask for any modifications just a door install in the bathroom. I would say customer service has been fairly easy with Newmar. Just make a phone call and they will talk you through it. We didn't visit Newmar or Tiffin or American Coach I just went with my gut on my purchase but did quite a bit of research over and over. When we did pick up the mh at Mt. Comfort and did our walk through the service tech did tell me a lot of Tiffin owners prefer that manufacturer because it drives like a truck and most owners are retired truck drivers, however I can't validate that because I don't know any Tiffin owners. Lastly, I am a big fan of family owned companies because of my occupation so it would has been between Tiffin and Newmar.
Congratulations again and have fun...
Safe travels, David