i'd do it, assuming you trust me enough to do it... i have a spare o-ring kit
i'll pay for anything in the (rare) chance i break anything moreso than its already broken, and you dont have to pay me anything except shipping. unless you want to donate a few bucks
i own a cocker, know them inside and out, have all the tools, and ive fixed other peoples cockers before. get on aim or send a pm, im never too busy to not fix something...