Hi. Total time to install obviously depends on CPU, disk speed, memory, if the software is already staged to disk, etc. But where most of the time is really spent is setting up the machine to perform the install (users, patches, etc), patches after the install (ex. 9.0.4.1 and security patch 68), and configuration (Apache, SSL, backup/recovery, etc).
If you've worked with 9iAS V2 and are going to 10gAS, I think you'll find the installation to be relatively easy. It may be a little faster, but the important thing is you'll have fewer bugs and problems to deal with. 10gAS has some strict installation requirements, but if you follow the install guide and meet those requirements you shouldn't have too many problems.
Thanks,
Mike