subs and screen

im looking into buying a 99 9-5 and i currently have a 7 inch screen and 2 12 in. subs in my jimmy. ive been reading some posts about aftermarket stereos in the forums and havent really gotten a straight answer... if i want to put this stuff in a saab will i have to do a bunch of mods and electrical work or will it be a straight swap? i understand that the steering wheel controls may not work but ive read that the car wont start...? i need some info please cause if it doesnt work i will sell the screen and subs with my truck. thanks

thats right up my alley I put a 7inch in my 03' 93 and 2 12's in the trunk heres the links

http://www.saabforums.com/m_2426/tm.ht

http://www.saabforums.com/m_3032/tm.htm