Hey guys it all depends what you want doing...But my thoughts are:-
Sending or bringing the units to me has got to be less expensive than me coming to you and doing the whole removal, renovate and replacement task?? We use a courier service at work that charges about £10 national UK delivery upto 25kgs...

Ebay 500 exchange units are £120 plus £25.00 carriage (delivery and old units return) = £145.00 total (with no extended downtime, as job is simply a swop over)
If you supply the King Pin Bush Kit with your old units I will charge £40 including return post....(with anticipated downtime of about 2 weeks)
If I supply the kit I will charge £105 including return post...
However, if you need someone to do the whole removal and repair job we would need to have a chat... [-/
Regards
Nev...