Hello and welcome to Beoworld.
From you description I don't think it is a Beogram 7000 which is a standalone turntable, I think it is a Beocenter 7000 details of which can be found here
http://www.beoworld.org/prod_details.asp?pid=404
It is a fine unit, I had one until earlier this year but it does take up a lot of space. Sadly it is true that the cartridges are expensive to replace but a new one from Soundsmith would last for many years before requiring replacement as the tracking weight is very low.
Assuming everything works (including cartridge) and the speakers are in good condition you are probably looking at £100-£150 for the whole package, or due to the way eBay works slightly more iif the components were sold separately. Maybe £80-100 if the cartridge is kaput.
Simon