Re: Which Manfrotto Tripod are you useing?
I have a Bogen/Manfrotto 055XPROB tripod with an 804RC2 pan/tilt head. A buddy of mine has the 055's little brother, the 190XPROB...same head. Both of these tripods will allow you to observe from the prone, sitting/kneeling, and standing positions with ease. The XPROB tripods have the horizontal center column that rotates out which you may or may not want/need. I use this feature when shooting prone. Deploy the tripod to one side, extend the center column out and over to my shooting position, then position the scope close to me so that I don't have to drastically alter my shooting position to spot hits on target or otherwise. It is a great feature!
The only real differences between the 190 and the 55 are the weight they'll support (due to the differences in the diameter of the tripod legs/supports). The 190 will hold around 11lbs (don't forget to add the weight of whatever the head you decide to install on the tripod when calculating how big a tripod you need) while the 55 will support around 15.5lbs. Those are Manfrotto's rating which are terribly understated. I have attached my PRS rifle cradle to my 055 and use it to support a 17lb+ rifle/gear without any issues.
As for a tripod head...that is your call. I really like how solid the 804RC2 head is on my tripod, but I have also used the 322RC2 grip head which I have been considering upgrading to for a while now (too many ideas and not enough cash to fund them all...sigh).
I would check out the tripods on B&H Photo/Video's website and get an idea of what you might prefer. They have excellent pics, reviews, etc. on their site, as well as a HUGE selection. BUT...with that said...before you buy, get with Doug and the guys at CameralandNY (a site sponsor here) and see what they can do for you. I will bet you that they will beat B&H's price and you'll be supporting "one of our own" by going that route.
GOOD LUCK!!