I need some STW advice on how to go about replacing my GXP bb and Truvativ crank with a new Race Face bb and crank.

I'm fairly confident I can do this myself as long as I can find:

1- a concise and definitive description of what to do, WITH pics would be a bonus!
2- what tools and materials I need

And do I just use the same spacers in the new bb as the old?

My LBS say that the GXP and raceface bb's are the same dimensions and it "should" be easy to do (unlike if I was planning to go from GXP to Shimano apparently…)

My LBS also said the frame definitely doesn't need to be re-faced, which tbh was news to me as I thought you "always" re-faced the frame when you replace the bb??

I'm not completely ham-fisted so as long as I can get a good description of what to do I may be brave and do it myself rather than wait 2-3 weeks for my lbs to fit me in!

Thanks in advance

either you misunderstood or your LBS has RF cranksets to sell. there's no reason why you shouldn't replace with shimano.
good move getting shot of GXP IMO.
you'll want a BB spanner whatever you do. if you go shimano you'll want the pre-load tool as well ( about 3 quid ). the crankset will come with instructions, spacers etc. etc. otherwise look up the park tool repair guide – you don't need to buy their tools, just buy what you fancy off of crc or wherever.
you'll need some grease too. 'bout it.

Thanks, so what about the re-facing?

only needs facing once (if that)

everything you need to know is here

I have a GXP BB in mine. The removal and installation is quite straight forward. Take a look on youtube for a vid. The only problem I ewncountered when I serviced my BB was the cups were really tight on and needed extra leverage from an old seat post over the BB tool. The tool it self was 13 quid. Get some good quality grease for the threads and be careful as to which side the cups go on.
Depending on the cranks you might need a crank extractor bolt. Mine had one already. There will be a 5mm bolt infront of a 8mm bolt on the non drive side crank to aid removal. Took me a moment to figur it out.
HTH

Go Shimano!The raceface bottom brackets are crap,mine lasted 3 dry months.
The Shimano is far easier to install and take apart.Only the raceface rings are better looking but don't seem to last any longer.

Both my sets of deus cranks now creak after about a year , dont think im alone with this either.

Shimano much quicker to fit no silly chain line washers to fiddle with.

But anything will be better than the gxp you have now

the park tool website is very good for tech advice