Truck Repair: ISB-275 thermostat, winnebago journey, crankcase breather

Question
I own a 2000 Winnebago Journey with a Cummins ISB-275. I had persistent problems with overheating in the summers, until I was finally informed (not by Cummins, btw) that the crankcase breather tube was too short (a design flaw) and oil was fouling the radiator - leading to overheating.  Cummins repaired this in Phoenix in 2003 and steam cleaned the radiator; and the overheat problem pretty much disappeared. Late last summer, however, the opposite problem came up. Now, the engine won't heat up at all (which means the dashboard heater stays cold - to my wife's extreme discontent).  I am assuming the thermostat has just taken too much of a beating with the repeated overheating for several summers, and it is now stuck in the open position.  

Assuming I've made a reasonable diagnosis, my question is:  How difficult is it to change out the thermostat?  Is it something that can be done from beneath my motorhome by a self-taught moderately skilled owner, or would you recommend I go ahead and have this done by a service center? Where is the thermostat located?  I am trying to find an online service manual, with no success so far.

Finally, what is your opinion of the Banks power booster systems?  The 275 seems a bit underpowered for my rig's weight, and I've becomed accustomed to patiently climbing all the mountains between the lower 48 and Alaska in lower gears.  I'm wondering if you think the Banks system (or any other similar power booster) would really increase HP enough to noticeably improve hill climbing ability.

Thanks for you help.

Keith Laurie

Answer
The thermostat is under the top radiator hose outlet connection.It requires no gasket.You only need a 8mm or 5/16 socket to remove the connection after you drain the coolant.If there is an access under the bed,this will be an easy task except for the leaning over part.As far as the Banks system,you could possibbly notice some improvment.