Yes you certainly can add electric start to your sled. I just did it on my wifes 2002 MxZ 500 LC. The kit cost $530US from the Doo dealer.
I bought a Doo clutch puller for $30 so that I had a good quality puller and I did the install myself - very easy if you are somewhat mechanical. Just my $.02.
2011 Ski Doo MxZ X-RS 800 ETEC
2009 Ski Doo MxZ-X 800R
2006 Ski Doo MxZ Renegade X 1000 SDI
2002 Ski Doo MxZ 800 Sport w/ 144 gold digger studs.
2002 Ski Doo MxZ 500 R Sport w/ 96 gold digger studs & electric start.