right, I swapped my lambdas to see if it made a difference when she was running really poorly, and it made none.. they are an identical part, therefore if the precat one can resist that sort of abuse, the after cat one can too.
also those sensors are literally a 15 minute job to change, just get her on axle stands, spanner on it, remember you may need to tap the spanner with a hammer to "shock" them out - JMS also gave me this advice as they can be a total $%$£ to get out by swinging on it - worked for me.
the ball joint I don't think I'd do myself due to the agro, so yeah get the garage to do that but ren7oaks quoted me 1 hour labour tops for mine.. so that's £40 + VAT for the hour, then the part.. ring renault, find out how much the part is, and get your lambda sensor from NW Performance's website for around 50 quid delivered.
all in I wouldn't expect to pay above £150 for the lot.
as for remapping, I think your mechanic has been exposed to too many exhaust fumes himself, either that or he thinks you're a total fool. either way if that garage is trying to have you over so badly I for one would never go there again.
as mentioned go rentec if you're close by even for small things, I travelled 200+ miles to get them to do my cambelt and aux belt change, they are a very recommended and reputable specialist on here.
