Well, when you say you been writing code for years, do you have any choice as to the final platform?
Access 2010 can create web based applications that scale horizontally in a HUGE way. The resulting applications don't requite Silverlight or even any ActiveX, but ONLY a standard browser. Here is a video of a application I wrote in Access, and note at the half way point I switch to running in a browser.
http://www.youtube.com/watch?v=AU4mH0jPntI
Access 2010 also now does have database triggers and stored procedures. However, you are hinting that you don't have a choice of technologies here so the above new features and even the new Web site creating ability of Access is thus moot for you.
I guess the 1st area I would start with is installing and setting up MySql. The MySql site has some good links to tutorials etc. You simply have to get up to speed with that database server and get conformable with it regardless of learning PHP anyway, so that one step and area I would start out with. And, if you worked with databases, then you find MySql quite easy to get up to speed with so you feel like you making some progress as you embark on this new road