what you're going to find is that you're in for a long uphill hike, not run. as well now suggests, as a 4:25 flatland marathoner, you can expect something like 7:00-7:30 for pikes peak -- if footing is good up high, and slower if it's not. just go with the crowd, enjoy the hike up, and take in the views.
for preparation, time on your feet should be the goal, including time spent hiking up the longest, steepest trails in your area (i regularly did multiples up a 1.5-mile forest road, down a 2-mile trail for long runs during my buildup). note that the surface of the barr trail is really quite tame, so there's no specific need to get good at dealing with rocks, roots, etc.
to set your expectations, the year i did PPM, i was a late-40s female 3:20-ish flatland marathoner and clocked just over six hours at PPM (4 up, 2 down, passing ~75 people on the descent); there was zero snow on race day.