i need some advice

a friend of mine offered me an 86 montero for free. i went and looked at it, and other than minor body damage, it looks fine. now for the problems, it needs a head gasket, a soft plug, and a passenger side window. it has 221,000 miles on it. i think its a good deal, but i want some input first. could someone please tell me how much it would cost, and how hard it would be to replace the gasket, plug, and window, or if i should just pass it up.

p.s. the wheels on the front are 14's, and the rears are 15's. should i get all the same size, or could i leave them on?