I have done a valley pan on a BMW M60. I am sure they are similar. Not hard, but tedious and not great if you are like me and trying to avoid back surgery - but that is a landcruiser and sits higher. Photograph everything to keep track.
Anything you take out that is plastic will be brittle, so be careful and I would not reinstall anything that is plastic - so on my car I changed the PCV while I had it out to take one example. Think I also changed the auxiliary water pump and dual valve for the hvac, but this was a few years ago. Point is, Anything that has to come out, or that you have good access to while the intake manifold is out, you should consider changing for improved reliability. I know this is a Toyota so everyone thinks nothing ever breaks, but while Toyotas are very good they age like everything else so a job like this provides opportunities for additional preventive maintenance on 15 year old car.
If you aren’t comfortable with the job, it’s probably 1k to 1.5k in labor at a good Toyota shop. That is not unfair price wise if you know what is involved and put some value on your own time.
Good luck, hth.