The boat looks just great. I'm a bit biased being a SeaRider owner but they are tough as nails. I have a 4.7 which is a US Coast Guard Model and looking at the very tough strakes on your unit, you got the industrial heavy duty unit. The hulls on these unit are heavy weather capable.
My tubes in the tropics are ten years old and solid. Yes, to answer a question, often the tubes are left somewhat under inflated or will seem that way early in the morning or during overcast conditions and will tighten up as the air expands in the heat of the day. Unless something horrible was done to your tubes, you should have no worries there.
I've read reports of transoms that were drilled and left unsealed allowing moisture to impregnate the wood core. Check any through transom holes for proper sealing and inspect for any cracks and observe for any movement, which you surely don't want to see.
I've got a Johnson 50 on my boat, Evinrude and Johnson are both built by Bombardier and are good engines. The engine discussions circle around either fuel economy, 4 stroke vs. 2 stroke and or WOT flat out speed and most people like whatever it is they have vs. all others but a properly maintained Evinrude is a good solid power unit. I would of course have the engine gone over by someone that knows what they are doing and give it a complete PM service.
You say somone nicked your axle
That's not nice!
There is such a wealth of information on RibNet that I am sure you will receive several good replies and if you look in this forum as well as Engines, Electronics and others, many many subjects are covered in detail.
Let me know how happy you are once you get going!