Your story sounds so much like mine. I also was seeing an ENT for leukoplakia and learned in January of this year it had turned to cancer. I had surgery on Feb. 3, much as you are describing: 1/3 tongue removed, floor of mouth removed, left neck dissection, flap using forearm flap, skin graft from thigh to cover arm wound. I did NOT have to have a trach or peg. I was kept heavily sedated for four days in ICU with breathing tube and feeding tube. I was out of the hospital in a week. Pathology showed clear margins on three sides of what they removed, but not on the other, so on the 27th back I went again for more surgery. This time they took the rest of my bottom teeth, part of gum and bone. I will get results of this pathology Friday.
I will be on a liquid diet a long time...the flap is very large, and pushes my tongue to one side. It cannot be "trimmed" until all healing complete (and if I do radiation that will mean some time), plus now I have no bottom teeth and that situation cannot be remedied until healing complete either.
Yes, my speech is substantially different although I can be understood. I echo what someone else already told you: record yourself. I wish I had done more of it. I did make a tape for my husband just before my surgery and he treasures it. I wish I had done so for all my children and grandchildren. When the "trimming" can be done, the doctors tell me I will speak plainer than now, but never sound as I did before all of this.
About radiation: my doctor had told me that he thought I would not have to have this. When I was released from the hospital this last time, his associates told me to expect it. After researching and reading the postings here on this site, I have about decided I WANT it. So for what it is worth...that is where I am at. Best wishes to you.