Welcome Lars!
There's a wealth of information in Rics both here, and as Kira has so kindly pointed out, on the RIC corporate website and forum.
The backbone of the Ric lineup is the 4003, which is essentially a modernised version of the 4001, which was itself a development of the 4000, the original Ric bass. In some ways, the evolution of the 4003 from the 400 is akin to the evolution of the P-bass - some big steps here and there with a bit of tinkering over decades has got us where we are today.
The main features of the 4003 are:
Neck through design (currently with a slim neck profile);
Maple neck and body wings;
Slim body;
Bubinga fingerboard;
Two hot (~13kohm) single coil pickups;
Funky retro housing for the treble pickup (complete with pickup cover);
Retro tailpiece;
Ric-o-sound - the ability to send a seperate signal for each pickup;
Full body and neck binding.
Soundwise, the 4003 is more "scooped" than a P-bass - brighter trebles and strong bass at the expense of mids with both pickups wide open. The pickup configuration gives great sonic versatility - you can really change the tone dramatically by judcious use of the controls and/or pickup switch. As the bass has single-coil pickups, there can be some noise issues. I find the single-coils to give more bight and clarity than humbuckers, so it's a trade off I'm happy with.
In terms of playability, the 4003 has a wonderfully fast neck (kind of like a J-bass, but not as tapered). Some find the treble pickup mount and cover to be a problem in terms of playing fingerstyle, but I've never had an issue.
In terms of looks, the 4003 is a great retro-futuristic beast. I've always felt it looks like a prop from a 1950s sci-fi movie set in 2050.
Reliability - I've never had a problem with my Rics that hasn't been self-inflicted (or tech-inflicted). Others have had issues with the tailpiece. In general, the build quality and hardware are top-notch.
The 4003 is the bargain of the Ric bass line up. Given the current economic circumstances, you may be able to find some great deals if you're patient. You should be able to snag a good
used 4003 for USD 1,400 - USD 1,600 (plus shipping, duties and taxes at your end) without trying too hard. You may be able to save $200 or so with a little more effort. New basses will be somewhat more expensive, and this can vary greatly with geographic location.
I hope you get to sample one when you're in Liverpool, then you can judge many of the subjective issues, like tone and playability, for yourself.
In terms of buying, EU dealers (sorry, I'm making the assumption that you live in the EU or nearby) should be taking shipments soon (unless they already have) so there will be decent availability of new stock. For
used basses, the first stop will be the "for sale" forum on this site. Then ebay, if you know exactly what you're doing (not for the faint hearted), then US dealers (provided US shipping costs are not too egregious) and Ishibashi in Tokyo (they often have some great 4003s in stock at reasonable prices, and shipping is cheap, though the yen is expensive right now), though you'll pay more at a retailer. To peruse a number of US dealers, check out
http://www.gbase.com/. Ishibashi's web site for used stock is:
http://www.ishibashi.co.jp/u_box/. Type "Rickenbacker" into the field on the left pane under the roman alphabet and you'll see their stock of guitars and basses. An English summary of their policies is here:
http://www.ishibashi-music.com/
They have a nice Fireglo 4003S (the "S" variant has no binding, no Ric-o-sound) for USD 1,650.
All the best!
but where i live there is no stores selling them and i dont know anyone who has one. despite this ive fell in love with rickenbacker. i love the sound of it. and i am hoping to try one out next week. (im going to liverpool) but there is a few things i would like to know, how is the best way to buy one. what is the differences between the model and the year. how much will i be likely to pay for one. 
