There is a Grand Exchange database on the Runescape site that you can get rought ideas from. I'll provide a link below for it, I would recommend bookmarking it for future references.
You don't buy oak trees. You can buy oak logs, or oak planks. You can also buy oak seeds, which in this case are called "acorns". Prices in RuneScape change all the time, since they are mainly driven by supply and demand. You can find updated prices here: at the top of the main RuneScape page, there is a kind of menu; select "Community", then "Grand Exchange".
There is no magic planks in runescape. Only plank, oak plank, teak plank and mahogany plank.
you can't get free oak planks on runescape now stop being a noob and make them yourself. -.-
There are 3-5 oak trees in rimmington
Yes if it's an oak woodland.
Willows are much faster xp (67-68) but you can only get a 30 gp per log. Oaks give you about 37 xp and are worth 68 gp each.
Cut oak logs
The Bonny Oak 15 stove from the Fuller Warren Company is worth $2900.
Oak longbows can fire up to Mithril By snerderwerder (nickname)
You can buy bagged oak trees from the Garden Supplier in Falador park.
near varrock west bank
An oak tree's roots are underground and anchors the tree to the ground. The roots also supplies the tree with water and nutrients. The branches support the leaves and acorns.