new to the game auto box pipes

I have just purchased my first disco after a landrover less life for the last 10 years. I've picked up a 300tdi auto P reg and have enjoyed it for a day until I found a problem! I thought a bit of power steering fluid was leaking but on closer inspection today it is gearbox oil / fluid I checked the gearbox fluid level and it didn't even register. The pipe that is leaking is some time of bodge job that runs from the oil cooler in from the the radiator and appears to be a piece of hose pipe with clips! My question is this can you by replacement pipes? Should I renew them all or just the obviously wrong one? SHould I take this opotunity to renew the outbox fuel filter (they seem cheap enough) and lastly is this a job I can do myself? If so what is the procedure i.e. does it matter if air gets into the system (I presume not) thank you in advance for the advice
Breakers

sounds like the piece i changed a month ago got from a independant £23

I may b wrong but the manual gear box oil cooler is in front of the rad the oil cooler along side the rad is for the engine.

Post a pic of the problem and I will look up the part no. for U.

As you say filters are cheap .. so change them.

I spoke to a independent dealer yesterday and think we have identified the pipe (around 30 quid) thank you for the offer of identifying the part though if he doesn't come through with it, I'll be asking again. Can I just replace it and the gearbox filter then top it all up? I presume so having read the posts on doing this. Is this a process I could ask my back street garage to do or woudl a specialist be better I don't have time with work to do it myself quickly and I need the vehicle back on the road.
cheers for all the advice

Depends which pipe it is if its the one on the side of the autobox it is doable but a right pain, I took my front pipe off to get to mine and it was still a pain to do.