For the majority of businesses out there not doing major e-commerce and pretty much sticking to in-house needs, I believe SQL Server is a great product. The support for it is tremendous as the user base is huge. The book I mentioned above is great even for beginners. SQL Server comes with the Northwind database, which, as an Access user, you should be familiar with. Accompanying with Northwind is the Pubs database, which this book uses both for several examples. My recommendation is to get a hold of SQL Server, load it up, and start playing with it. It is VERY extensive and will take you a lifetime to learn it all, so don't get discouraged. You can learn the basics in no time and get your Access front ends to the next level relatively quick.
Of course, feel free to post questions here and I will help when I can. The only thing I ask is to first look in Books Online, do a quick Google search and search this forum with your question. Chances are, you are not the only one with your issue. But if you do post and I or someone else is able to respond, please do so in kind either providing a quick, "Thanks! That worked" or "It's not quite what I am looking for" or "I found the answer, I had to
explanation ... or whatever. Many other people also come and search these forums and it is nice to have the resolution there. Nothing drives me crazier than when I am searching for an answer and the original poster doesn't post whether they were able to find a fix.
Also, I don't get paid to help, so my payment is to hear that I was helpful.
Don't mean to get on a soapbox here, well, maybe I do, but ...
Where in Colorado are you? I lived in Loveland and Ft Collins for many a year. Great area.
BTW, I use ApexSQL Edit for my editor. Great Tool for writing code.