rads are fairly easy to replace TBH, its a simple case of jubilee clips and if you have never done it before going slowly.
things to be careful of..
1) be careful with the new rad when putting it in, its normally a tight space and they are easy to damage.
2) put the correct amount and right spec of coolant, the pink one is what we use in the JTDM, you don't have to buy paraflu just the pink one from ECP or shop4parts..
3) the system is self bleed so it should just work itself out but you must make sure there is little or no air in the system, get the coolant quantity and pretty much fill up and keep an eye on the level for about a week or so..it will probably need topping up a few times before it stabilizes.
oh and you don't need an OEM rad either this one will be just fine.
have some new jubilee clips ready to go and you should get this done a good bit for less than £100 and a few hours of your time. I can now do a BMW e36 rad change in about 1hr, it will take you a few hours the first time but best go slow and get it right.
good luck and enjoy the feeling of doing it yourself and avoiding a likely £250+ garage bill.
p.s I don't wish to scare you but its a good idea to look through the history and make sure you have an idea of WHY the rad has failed, if its still the original rad then its just likely to be wear and tear,if its had a couple I would be slightly concerned and any more would hint at an underlying problem.
its probably nothing but a banjaxed rad but do check the history before throwing parts at it.