Should I attempt to change these myself, or pay someone a small fortune to do it for me?  I've got the forks, I've got the seals, all i need to do is buy the oil and I'm away, but how hard is it to do?                                                                                                                                                                             

Depends on the bike Seb. You need to keep a very careful eye on which sequence the various cartridges/shims and crush washers are stacked in. Get one wrong and you can end up with far worse suspension.   Normal upright forks should cost about £50 to have the seals done as a competent mechanic with the right kit can have them done in about an hour for a naked bike. Some faired bikes take longer because access to the lower yoke clamp bolts can be very restricted.   While the forks are out it is wise to strip and clean the front calipers too as access to those will be better.                                                                                                                                                                             

 Don't try to do em yourself. If you've allready done a set ok, but like GH said there's so many differant types, and most of em have some kind of little booby-trap for the novice!! I help someone to do mine, wether its an off-roader or a Pan Euro, you nearly allways seem to need five hands to make it go right. (Ohh,.. and patience too)!

Or take them to Maxton like I do!  They'll respring and revalve your forks specifically for you for about £150 and you get new seals for free!   The difference to my CB was staggering.   Or you could do them yourself.  I think anyone reasonably mechanically minded can do fork seals.  I would recommend getting a manual and as the gents above have said take very careful note of what spacers, shims and so forth go where.   Simple tip; do one fork leg at a time and as you dismantle the fork legs lay any loose parts (if your bike has cartridge forks then things like the shim stacks are probably held together) in the order they come off on a clean flat surface.                                                                                                                                                                             

Hey Geoff........I didn't know Maxton made girders!             (runs...........)                                                                                                                                                                             

I changed mine myself with the help of a friend... well I went shopping whilst he did em in enough time for me to purchase a pair of shoes and handbag. x                                                                                                                                                                              

Seb, if you do it yourself, one thing that might screw you up is the alan bolt that holds the inner parts in place, you may need a long extension for your socket (the nut inside can be a funny size and shape) to reach the bottom of the inner fork. Last one I did i got a 56 com length of Hex bar to do the job on a yamah. It isn't difficult if you have all the tools and as has been said in a previous post just lay it out one piece at a time and clean and inspect as you go....you may need new locking washers and rubber ring seals for the top of the forks depending on type of forks.....   ...remember loctite for the bolt in the bottom of the fork leg...you don't want it coming out,and a small length of tubing and mark of the tube with tape for depth of oil and a syringe to level the fork oil, there are plenty of web sites that will walk talk you through it...   ....but if not most bike shops will do it if you take the legs off and take em in for around £50, and don't put cheap seals in they don't last a damn.                                                                                                                                                                             

Best thing to do is watch someone who knows what he's doing so that you can do it yourself the next time. 
Seeing as you posted the question back in December, you've either done it yourself or had it done. How did it go?                                                                                                                                                                             

lol didn't notice the date of the post.....lol                                                                                                                                                                             

do it your self seb simple enough just might need to get or make a tool or two   i help yorkshireman last year with his they fine as far as i know  dont think hes gone though a hedge yet !!