7 Year old domain bang on topic

[burcot]

Hi,
I have just been given a free hand to optimise a 7 year old Dmoz listed PR4 site.
The site has been neglected and consisted of homepage two working pages and twelve 404 error pages.
The site is exactly same topic as my own e commerce sandboxed site.
I can add links on any new pages that are developed.
Today I changed the title of the homepage from company name to
keyword and killed the 404 pages.
By coincidence google indexed the homepage one hour later
Few hours after Gbot visited site ranked #20 for widget and #1 for
deluxe widget.
I knew google liked aged domains but I can't believe how fast this happened.

I would really appreciate your thoughts on future optimisation efforts, don't want to trigger any filters, so any advise on link building frequency, content and page building rate etc would be great.
Also I am not sure how many links to my own site I should add.
Should I add relevant link on each page ie linkfrom widgets to my widgets page, link from red widgets to my red widgets page
or is there a maximum No of benificial links.

Hope you unerstand my babbling and don't consider this thread
far to long for a newbie

Cheers