My advice: Go for it!

It's a great area to hike in.
I think the "standard route" from Idyllwild would be to start in Humber Park, go up the Devil's Slide Trail, turn left at Saddle Junction, head to Wellsmans Divide, and then from Wellmans, head to the summit. Plenty of other routes from the west including the Deer Springs Trail, Marion Mountain Trail, Seven Pines Trail, and Fuller Ridge Trail. From the east, going up the tram, and then heading via Round Valley and Wellmans Divide is the standard route.
If you go to the Mt. San Jacinto State Park web page, they have a pdf that you can download which is a
map of the area that includes mileages. If you hike frequently and are in good shape, then the summit shouldn't be too bad, although the altitude can be tough if you're not used to it. If you're not sure you can make the summit and return all in one day, you might try something like Tahquitz Peak via the South Ridge Trail just to get an idea of your time and how you handle altitude.
Just some thoughts,
HJ