Welcome. Rhinos last quite a while if you take care of them. They are work horses. There's guys on here that I have heard have over 9000 miles on them and they're still running. As for 38mph that's what they are limited to from factory. If you want a bit more speed then you need to start adding some mods. Aftermarket clutch, sheave, clutch weights, CDI, fuel/ignition controller, etc will all give you more speed. The CDI will make the most difference right off the hop as it will take way the factory speed limiter. I'm not sure what you mean by a "free wheel gear". They are usually either in 2wd, 4wd high, 4wd low, 4 wheel locked. The rear diff is always locked whether in 2wd or 4wd. Regular maintenance is good so yes, check your belt and clutch if the machine is new to you. As for oil changes I typically do one every year. Depends on how much you run yours though. If you are planning on putting a lot of miles on then change the oil more frequently.