You won't be able to sit for a month after you get done kicking yourself in the arse for doing that.
The 250f will feel very flat in the dessert. Most likely you will end up on the rev limiter, in sandy conditions, on a bike the feels slower than what your on now. You'll be doing alot of maintenance.
Don't get me wrong, the 250f has it's strenghts. It's not made for the desert, or to keep up with a 250 2t in drag race. They are easier to ride than a 2t, smoother. Mine is almost electric-like in delivery. In the trails and on the track this bike suits me MUCH better than the 02 RM250 I had before it. The RM was FAST. I am NOT FAST. Well, unless we're drag racing in the open. Which is why I made the switch. I ride with the guy I sold the RM to and I shed a tear every time we come out of a corner (he's usually behind me) and into a straightaway and he rips past me with front wheel off the ground in fifth gear. This is usually followed by some degree of loss of control and quite often results in some personal injury. We both suck at riding, and I crash ALOT less on 250f than did on the RM.
Lol, I'll shut up now. I say get a newer 2t, have you considered a KTM300? The problems you have with your bike are mechanical and fixable, not traits of a proper running 2 stroke.