The only mechanical problem I had was when my chain jumped off once while I was moving into a lower gear. It's a weird feeling to be pedaling and suddenly have no gears. It was a quick fix at the side of the road.
Good ride!! Truly, 50 miles will seem easy, now that you have 25 under your belt.
In regards to the chain, if my chain has slipped of the small chain ring into my frame, I just shift the rear cassette to the outer-most cassette (the smallest one) and keep pedaling, and wow!! the chain goes right back on. Or, if necessary, I stop, do the same thing, and lift the rear of the bike up, turn the pedals, and it goes right back on.
If it happens too much, you need an adjustment on the limits of the front derailleur.