not all mac amps use the same type of bulbs,some are like mini car blinker bulbs & just pop in,others are soldier type & some are connected to a very small peice of green board.
the mc150 uses the type that is connected to green board,the green boards are attached by small phillips screws & come right out,all you need to take apart the amp & green boards is a #2 phillips screw driver & it takes about 1 hour to take apart the amp & remove all the green boards & the same to put it all back together,if you order a new set of bulbs from mac im pretty sure that they dont come with the tiny green boards.
i had a mc150 that needed most of the bulbs replaced & i took out the bulbs with the green boards attached & took them to a local tv repair shop for replacement,i didnt want to chance screwing up the green boards soldering in the bulbs.
the repair cost me about $10 & the tech did the work while i waited,the tech also told me that type of bulb is a standard shelf type bulb that any tv repair shop should have on hand .
ive had great luck using tv repair shops for bulb replacement on all my mac gear,their happy to get the business & you dont need to leave your gear for weeks plus it costs a fraction of what hifi shops charge to replace bulbs.