Mole -Welcome to TalkBass. Hope you find it rates your further involvement.
I am not a dealer, just someone who has been playing since the Beatles first came to the US and showed up on The Ed Sullivan Show.
My advice is to determine your budget then start looking for what fits, if you haven't already. Then, get as many catalogs sent to you as possible so you have something tangible to think over. If you go to
www.gearsearch.com they have several big dealers with mail order catalogs. Some are listed at the top of the page or you can use their search for "bass." There are many other sites, but that would be a start. Or, you could just plug the word "bass guitar" into a search engine and find a multitude of sources.
www.bassplayer.com is the standard rag that many of us suscribe to.
Then, I suggest culling some possible bass/amp candidates and putting up a thread here at TalkBass and tell us what makes/models you are considering and finding out what other TalkBassers' experiences are with these potential choices. Not many exist that one of us hasn't either tried/owned/used.
As for the "big change" you are worried about, you could either try some out at a music store and see what you think, or rent a setup which would let you see if the instrument is a good fit for you.
One word of caution - once you start, you can count on your bank account struggling to stay in the black, as many of us tend to get GAS, (Gear Acquistion Syndrome).