Phatal, let me see if I can answer some of your additional questions:
>> what do you think about a price?
Sorry. Can't help you much here. As with so many things, you need to consider this in context of the condition of the amps and the price of your alternatives. Audiogon's Blue Book service might be of some help. If pushed to offer a guess, I'd say somewhere under USD$3,500 at this point, but that's just a guess.
>> how do i know if its been retubed?
You'll have to just ask the seller. The right question is "how many hours are on the existing tubes." The output tubes should be good for 4,000-6,000 hours as a broad rule of thumb. Conrad-Johnson still sells a complete replacement tube kit of this amp. So, you could check with them about the cost of the tube kit to know your expense risk.
>> what questions should i ask the seller?
Ask if any modifications have been made, if so by whom? Ask if the seller has the original shipping crates (always a good indication of a careful owner, imo).
>> these amps are massive 80lb.will they need a fan to cool them?
No, air cooling is all they need with adequate ventilation. They will put out some heat, so they will need several inches of open space around them, with 6-8" open space above them. For example, don't put them inside a closed cabinet, don't put them in an unventilated closet, don't put them on shelves with another shelf immediately above them (see above), don't stack them on top of each other :-), etc.
>> what tipe of care do i need to know?
Tube amps need fairly little care beyond checking the bias of the tubes every 2- or 3-months (depending on how much you notice it change) and replacing the tubes from time to time. Bias indicators are built into the amp, so biasing is very simple. (Explanation: "biasing" adjusts the electrical circuit to match the tube and as the tube ages, the circuit needs a slight adjustment to re-match the changes occurring in the tube. The adjustment is made via a small set screw, and you turn the screw until the bias indicator shows you're at the right point. In the case of the Premier 5, I think this indicator is a small LED: the light comes on when the bias needs adjusting, and goes off when correctly set.) Once you can no longer set the bias correctly, you definitely need to replace the tube(s); but, the tube can subtly degrade in sound quality even though you can still set the bias. You just have to be aware of any sonic degradation. If it sounds good to you, and you can bias it, it's pretty much OK unless you're getting pretty picky. Often the change is subtle and over a long enough period of time that you don't realize it until you install new tubes and hear the contrast. This is generally not something to obsess over.
>> sorry about all the questions, but im new to tube amps.
One other thing to consider is whether you really need a 200w amplifier for your speakers, particularly if tubed. My experience is that you generally can be very comfortable with a less powerful tube amp than solid state amp. A tube amp in the 70w-120w range would probably work very well with your 805s.
Happy to try to help! Good Luck.
Phatal