Hi Paul,
I also had similar problems with a BG1700 when I bought it a few years ago. There are a number of threads on this site about making adjustments to and lubricating the arm lifting mechanism on arms like the one on the 1700. It is a relatively straightforward job which even I managed to do successfully and I am totally inept! You may not need to take it to a dealer/repair shop at all.
If you don't have the original box, entrusting a radial-armed turntable to a carrier can be a risk, although once again there are a number of threads on site with very helpful suggestions. I sought advice on transporting mine by car (see link)
http://forum.beoworld.org/forums/t/26284.aspx
As for comparisons between it and the BG5000, they are both excellent turntables. Arguably, they are the best sounding radial-armed Beograms. (I'm not including the Thorens-based 3000 here!). I've not heard a direct comparison, but I would suggest the major differences are more about facilities on the BG5000 (light, remote capability) rather than sound. Also, most of the advice on site says the the BG5000 was much better made than its replacement, the BG5005 and all the subsequent tangentials up to the last, the BG7000.
The BG1700 is really robust, as well as being in comparison to the 400X Beograms very straightforward and uncomplicated. I have an MMC20EN in mine and I couldn't tell any difference between it and my BG 4004 with the same cartridge.
Lastly, I can see reason why the BG5000 shouldn't work with an MMC2, but if you are going to get the stylus redone anyway, it probably wouldn't cost much more to have it done to MMC2 specification.
Cleve