Advice for newbie on Tube gear


I'm seriously condsidering getting into tubes (valves here in UK).
I saw & heard them once at a hifi show & have been fantasising ever since.
I'm a bit tech illiterate.
I've been offered Sonic Frontiers SFL-2 preamp + SFCD-1 CD player (240V) for US$2200. Cond is v.good, tubes are about 18mths old. I'll probably buy an ss power amp also(below $700 used).
I'd appreciate any advice on what I'm letting myself in for :
How difficult is it to find & change tubes , How will I know when tubes need to be changed , How much will it cost , What else will I need to do (biasing???, capacitor replacing...).
Are tube SF units low maintenance? I don't really have much spare time ,and am easily confused by techy things.
My system : nothing left apart from AQ Diamond X3 i/c's, AQ Sterling spkr cable, and an old pair of excellent highly sensitive (96db), hi-end(ish) French speakers - Helius Sirius II (only a few made in the '70s/'80s).
sporter2
"I'm seriously thinking of getting into tubes" "I'd appreciate ANY advise on what I'm letting myself in for" Sounds like a general question on tubes to me?? Mabe my response should be go ahead and buy this stuff- you might like it, you might not but thats ok, it's your money not mine. I say go for it! Ya right. uhg
Sincere thanks to each who's posted a response (5 at the time of writing).
There must be many who've benefitted from these answers (I previously hadn't found all these answers on these forums - simple though they may be, but VERY informative to a novice).
Each suggestion/information has genuinly been helpful to me ... 300B's, Eldartford's experience, Sbanks explanation of the tubes and biassing, the TriodeGuild site, and Viridian's excellent to the point explanation of my particular situation.

I feel that I may be able to tackle the tube buying/replacing fear, and cope with the biassing (not so confident). I'm hoping I may be able to get away with doing minimal maintenance with the tubed pre & CD, and may even look into SF's own power amps (SF80..?).

Meanwhile I'm going for the SF tubed pre & CD (They look so good together I can't separate!).

Many many thanks!!!
Mahandave, maybe it was a general question on tubes. Issues on changing/buying tubes + biassing were answered, as well as other suggestions. I didn't find those specific comments/explanations elsewhere. Opinions were welcomed - sarcasm was not.
Viridian has it right, and the SF components are well-regarded, so I think your decision to go for it will prove fruitful. If your previous SS digital source and preamp were on a par with the $700 SS amp you propose to buy, than I suspect that the SF gear will be much superior. If the pair was retubed only 18 months ago, you won't have to worry about new tubes for at least that long again (barring a faulty or damaged tube). Enjoy your new gear!
Your choice of a preamp is fine - very high quality stuff and should last a long time if its in good shape. You mentioned the SF 80 tube amp. I have had one in a second system for the last 8 years - this is an excellent choice for the prices i see them going for on the internet. The choice of small tubes and power tubes available will allow you to dial in the kind of sound you want from detailed to warm. Its an absolute snap to bias new tubes and is good for a beginner to expirement with. Good bass - lots of power. Sounds more typical of older tube amps than the later models. However, be sure that you have a good local repair facility - if you need service you don't want to have to ship this to canada. Enjoy...