You will want one of these to get the front sprocket off...
http://www.machinemart.co.uk/shop/pr...C=GS-060810610
Probably the best power tool I've ever bought ^
Also, I presume you aren't going to actually order service parts from Germany. Try Wemoto instead, looks like about �100 for a chain and sprocket set.
Why 525? Or did you mean to write 520?
These are the best chain riveters I've ever used...
http://www.demon-tweeks.co.uk/motorc...-riveting-tool
However the cheaper ones they sell in Machine Mart are adequate, and what I use. I only use them to rivet, waste of time trying to split the old chain, just cut it off with an angle grinder
You can usually reuse the tab washers a few times before the tabs fall off, but it's worth having a couple of spares around.