i have just replaced my pump/motor assembly in a post 1997-2003 aquastream shower unit,i bought it from trading depot.co.uk £54.63 plus vat and postage,it came with full instructions and an installation kit.
basically you have to saw through the plastic pipes at the top of the unit to enable removal of the copper pipes which were preventing the pump removal,the copper pipes just pull out.
new plastic elbows come with the pump.
i smeared all the joints with fernox Ls-x joint compound to ensure a leak free job.
the job took less than an hour.
good luck
paul
January 2010