Well, you probably should start by getting familiar with Linux, as thats the native environment. Its not harder than W*ndows, just different, but more of it happens on the command line (which is like the MSDOS app) and its best to be familiar with that.
To try Linux, one of the "LiveCD" 's (such as Knoppix, Gnoppix, Mandrake Move, or PCLinux) will boot from CD image on a Windows machine without affecting the HD, and allow you to play around. I like PCLinuxOS (http://www.pclinuxonline.com/pclos/index.html) or google the others.
There was some talk of setting up an OpenACS LiveCD but I'm not sure about status/who/where. Try (http://www.sussdorff.de/oacs5dot2v2.iso), you may have to SaveLink As to get the download. This would be the easiest playground.
Alternatively, if you can find a spare box somewhere, load up a Linux distribution. No matter what anyone says, installing linux can be tough. so if everything doesn't seem straightforward, persist.
I've found Mandrake to be relatively easy, and usually successful, especially on newish hardware, but others will have their own views. Red Hat/Fedora, Debian, SUSE distributions should also work fine with OpenACS and have adherents here. Other nominations welcome.
Then follow the OpenACS intsall instructions (rather daunting but comprehensive). (https://openacs.org/doc/openacs-5-1/acs-admin.html)
If you don't want to do that, you could get a hosted OpenACS site to play with. I use and recommend Acornhosting for a low cost/ low volume site (http://acornhosting.net/) so I suggest contacting cathy -at- acornhosting.net.
There are other hosting company options try https://openacs.org/community/companies/
Tutorial in the main documentation,(https://openacs.org/doc/openacs-HEAD/how-do-I.html) problem sets in https://openacs.org/education/). Jade Rubick has numerous useful articles (http://rubick.com:8002/openacs/) notably (http://rubick.com:8002/openacs/getting_started/).
The basics are that content is in *.adp files, SQL in *.sql files (Oracle or Postgres) and functionality in *.tcl files.
If you're coming from MS Access, remember that Postgres is client/server, so you can access postgres databases from MS Access using an ODBC connection (with a few tweaks). But you shouldn't need to.
