Same as you but I am 46, made it up (barely) last August on an overnight. I mtb'd all summer to get my lung capacity up & did some short day hikes the month before with no pack. It was the hardest physical thing I've ever done although it doesn't seem like it now as I sit here on the couch. The altitude made me feel sick, but my feet! Shoes that were normally fine hurt coming down. Have good shoes. My pack was 33#.
As illustrated in Wilaby's response, nothing replaces work in the high mountains for a couple of reasons. 1.) You find out if you are going to get sick 2.) The experience and knowledge you acquire about what it takes to hike at and to these elevations.
My circumstances were similar the first time I came to MMWT. Worked my rear end off all summer, barely made it and did not go really high before going to Whitney Portal.
More that is between the ears about hiking in these environs, the better chance you will have to succeed.